View Full Version : Stroking a 401
I'm having the crank of my 401 off center ground to accept a 2.1 inch sbc 6 in rod, should get about 3.817 inch stroke. Plan to use a Wisco piston, anyone else tried this? Will have to remove about 4 - 6 cc from combustion chamber to keep compression ratio down to 9.3:1. Any thoughts?
jeepsr4ever
03-06-2004, 04:33 PM
are the pistons you are using forged, have you done any oiling mods yet, who did your regrind?
Yes the pistons are forged. I am going to install the valley oil mod. There is a really good machinist here in Great Falls, MT. He has built several engines for tractor pull comps when he was in Ioha.
Lifted79CJ7
03-06-2004, 08:19 PM
Hey J20, Welcome to the board! If you can, take lots of pics and and do a write up for us. I would love to see how this thing turns out! :sa:
Jack
A write up sounds like a great idea, could prevent others from making a few of the mistakes I made in finding and purchasing an engine (fortunatly very little $ involved, mostly time). If there is a moderator reading, how and where would you like to see this? I've learned a lot about engine geometry researching a rod/piston combo, cross sectioned a head to figure combustion chamber modification, and a few other things for this build. Could post pics also. Please point me in the right direction. Does this have a spell check function?
Elliott
03-07-2004, 10:13 AM
I've read you could do that using SBC rods and 400 pistons, don't know anymore then that other then I'm looking at a similar project with 4.150 stroke and 4.374 sleeves for 500CI. I guess it's workable. :mrgreen:
Elliott
03-07-2004, 10:58 AM
Here's some good interchange info you may want to rat hole somewhere:
http://www.american-powersports.com/dave/image/amx/tech/amc_pi.htm
I looked at the idea of sbc 400 pistons. Several problems, two of the most significant are: compression height is wrong and valve pocket angles are wrong. I called Wisco and Ross and both said pretty much the same thing. Also the 4.165 bore considered, with a 4.125 400 piston dictates for minor .020 bore on the 4.165 = 4.185. The 4.125 at .060 over is the only real possibility. But, considering the other problems, this still won't work. Another thing to consider is the clearance under the piston for the end of the connecting rod. The standard sbc dish is not big enough for the 58cc AMC heads. To get a 9.3:1 compression ratio, the piston dish needs to be 37cc. (I know there is a little room if head gaket thickness is adjusted and there is some room to work with quench) There is not enough material there for such a big dish. Combustion chambers must be opened up 4 tp 6cc to keep the piston dish at no more than 33cc and that is on the edge. One advantage of using a custom piston, is the ability to select a more efficient combustion shape. The machinist has ideas for this I'm not up on yet. As I get more info I'll post.
jeepsr4ever
03-07-2004, 04:15 PM
how about in the how to area I will sticky it for you....wish I had pics of my builds :smile:
Here is a question. Is there a production head that will fit the 71 - 78 AMC 360/401 (omit 304 to avoid valve size issue) with a bigger combustion chamber, say 64 or larger cc? I'm not aware of one.
20 May 05. The Edelbrock aluminum head is also a 58cc combustion chamber, stock valve size. I think Indy makes an aluminum AMC head with a 62cc combustion chamber. Very expensive, intended for high rpm applications.
jeepsr4ever
03-08-2004, 02:20 PM
maybe after porting but never a stock head
ILUV2XLR8
03-09-2004, 07:36 AM
Hey J20, just like to say hey! I may be in the Springs now, but I was borne and raised in Billings, MT. Good to have you aboard.
OK, lets move this to the "How To" page. I've got pics to post.
The way I figure it, I've got 9.208 inches of block to work with that being the distance from the center of the crank to the top of the cylinder. The 401 starts with a stroke of 3.68 inches, a 5.85 inch connecting rod measured from center of rod journal to center of piston pin and a 1.508 (about) compression hieght on the piston measured from the center of the piston pin to the top of the piston. Take half the stroke, 1.84 + 5.85 + 1.508 and you get 9.198. This leaves .010 at the top of the stroke for rod and piston expansion. Also consider the thickness of the head gasket so there is a little more room before the piston hits the head). Given all of that, I think of the stroke as the diameter of the circle the center of the connecting rod journal makes as it rotates around the crank center. to make this circle bigger I'm going to off center grind the connecting rod journal, reducing the connecting rod journal diameter from 2.2474 to 2.1 inch (same size as sbc rod). This will move the center of the connecting rod journal .0737 (2.2474 - 2.1 = .1474 now divide this by 2 and you get .0737). The stroke will increas by .1474 because the diameter of the circle the center of the connecting rod journal makes as it rotates around the crank shaft center will increase from 3.68 to 3.8274 (3.68 + .1474 = 3.8274). The radius of circle increased by .0737 so diameter increases by 2 times that or .1474. That is how I intend to increase the stroke of my 401. It may not come out exactly 3.8274 because the connecting rod journals have to be turned to take out a few very minor scratches. Lets say we go .010 on the connecting rod journals, I'll end up with a 3.817 in stroke. Either way, this engine will stomp all over a sbc 383!! Any body see any flaws in my thinking? I'll deal with the compression ration next because if the stroke gets longer and nothing changes with piston or head, compression ratio goes up. I'm aiming for a 9.2 : 1.
Elliott
03-10-2004, 06:59 PM
Fella ran these 401 4x4 stroker #s for me on Dyno 2000, it's based on ICH's Bracket Master Moldex 4.15" stroke crank and std bores (I have not confirmed with ICH that this crank will stuff in a factory 401 block):
The Moldex crank used in the Indy "Bracket Master 500"
is 4.15" stroke,
probably safe to say that is probably the largest
stroke we will see for a
stock block (assuming the 401 block can be massaged to
clear those crank
throws). That nets 452.3 cubes with the 4.165 bore,
and 600 ft/lbs of
torque at 2000 RPM!!! (with Ultradyne's smallest
hydraulic (.517/.541 lift &
231/239 duration) AMC cam, stock big-valve dogleg
heads, stock intake,
600CFM 4bbl, small-tube headers w/mufflers, 10.2-1
compression). Not much
HP there, but loads of torque. I also tried adding
fully ported heads,
big-tube headers, big cam, big carb & Torker, the
rev-range is dictated by
the bore/stroke ratio, and 5500 RPM is peaked-out for
this one, no matter
how much cam, exhaust, or intake you throw at it.
Engine Power Torque
RPM (Fly) (Fly)
2000 229 600
2500 266 559
3000 304 532
3500 327 491
4000 320 420
4500 296 345
5000 256 269
5500 207 198
jeepsr4ever
03-10-2004, 07:07 PM
thats some torque there! I know ive ripped crank bolts before but my goal this summer is a real stump puller!!!!!!!!!!
WOW! Those are very impressive torque values. I'd be interested to know what rod piston combo a build like that requires. My goal is not so lofty. This truck gets drove everyday. I've opted to use a 6 in sbc rod and a standard 3 ring set on the piston. A chose the six in rod to maintain a good rod length to stroke ratio. (1.59 : 1 stock 401, 1.6 :1 for 383 sbc) I know there is debate regarding the use of longer rods and I believe a longer rod is the better option primarily for the following two reasons: With the piston pin set higher in piston (There is a limit, I don't want to have to contend with supported rings. I think 1.25 in comprssion hieght is about as short as I would want to go.) the side load pressure the piston exerts on the cylinder wall is reduced, The variance in connecting rod angle in relationship to the connecting rod journal is minimized with a longer rod thus reducing the ovalating stress placed on the connecting rod bearings. I believe these two factors will increase engine life and reliability. Any thoughts?
http://hometown.aol.com/bpburner/J20homepageindex.html
Posted a few pics, I think. Some may find value others may not. The cross section of the head shows there is plenty of material to remove at least 5 cc.
Working with Wisco for a piston. Here are a few of the things discussed: The block should be bored to a "standard" bore to make use of a "standard" ring pack. Example, 4.125 + .060 = 4.165 + .020. There are a few more examples that will work. This has a few advantages, cost being a big one. Wisco is happy that the combustion chamber can be expanded at least 5 cc. This allows a small enough dish to leave enough thickness between the bottom of the dish and the top of the connecting rod. The exact shape of combustion chamber and dish have yet to be determined. I think the compression height will come out very close to 1.2 in., close to the proven sbc 383 (1.120) with 6 in rod.
A couple of new tidbits. I called ARP (very helpful) asking about AMC main studs and why they were not listed. It so happens that the AMC 401 main bolt measures 3.5 inches from under the head to end and is 1/2 in, same as ch*vy big block. I'll use a set of ch*vy big block two bolt main studs without windage tray. Saved a few $$ by going this route. Also, ordered a set of hardened push rods, just so happens ch*vy small block push rods are identical, ask for ch*vy sb push rods, saved a few more $$. The Scorpian roller rockers arrived, they are beautiful, it will be a shame to cover them. Went with the ARP 7/16 thread diameter top and bottom rocker studs. Will have to re-drill/tap bolt holes and mill down for guide plate. Have not ordered guide plates. Piston design will go final late next week.
Elliott
03-14-2004, 09:22 AM
WOW! Those are very impressive torque values. I'd be interested to know what rod piston combo a build like that requires. My goal is not so lofty. This truck gets drove everyday. I've opted to use a 6 in sbc rod and a standard 3 ring set on the piston. A chose the six in rod to maintain a good rod length to stroke ratio. (1.59 : 1 stock 401, 1.6 :1 for 383 sbc) I know there is debate regarding the use of longer rods and I believe a longer rod is the better option primarily for the following two reasons: With the piston pin set higher in piston (There is a limit, I don't want to have to contend with supported rings. I think 1.25 in comprssion hieght is about as short as I would want to go.) the side load pressure the piston exerts on the cylinder wall is reduced, The variance in connecting rod angle in relationship to the connecting rod journal is minimized with a longer rod thus reducing the ovalating stress placed on the connecting rod bearings. I believe these two factors will increase engine life and reliability. Any thoughts?
1) Those figures were just a dyno build, so don't know if the rod/pistons are compatible with the correct quench. Essentially the rods were 6.2x2.10 Eagles and the piston would be a flat top Std AMC bore piston @10.2:1 comp. I haven't determined a combination of pistons and rods that will fit that stroke length inside the deck height, looking at Mopar stroker flat top pistons in a larger 4.375 bore. :wink:
2) From what I've been reading ( http://victorylibrary.com/mopar/rod-tech-c.htm ) you are right on all counts... except one on the longer rod and rod angle benefits, the longer rod also builds more torque down low with a sacrifice at the top end.
3) FYI, I was looking into the Wiseco pistons because ICH uses them in the 500 Bracket Master.... I've been advised against them in favor of Ross and JE. Apparently they haven't held up that well... might want to get some more opinions on that from guys that are using them.
Elliott
03-14-2004, 09:35 AM
I'm having the crank of my 401 off center ground to accept a 2.1 inch sbc 6 in rod, should get about 3.817 inch stroke. Plan to use a Wisco piston, anyone else tried this? Will have to remove about 4 - 6 cc from combustion chamber to keep compression ratio down to 9.3:1. Any thoughts?
Just in case you want to crunch some more #s, that crank supposedly can be offset ground to throw a 3.93" stroke.
Elliot, you are correct. If you start with a 2.2474 connecting rod journal and off center grind to accept a sbc small journal rod (2.0) you can get a 3.9 inch stroke. I chose not to use the 2.0 journal because the ch*vy engineers must have known what they were doing in not using the 2.0 journal on the 350/400. I think the 2.0 journal was mainly a 283/327 thing. The extra .1 inch of stroke also shortens the compression height by .1 and jeopardizes the use of a standard ring pack, raising the cost of the piston. I don’t want to take the compression height to less than 1.2 inches. Want to leave plenty of metal for the ring pack.
Elliott (I spelled it right this time. I also miss spelled Scorpion in the previous post and I’ll bet there are still people looking Ioha. I meant Iowa.) Thanks for the data. I think a flat top piston in a standard bore 401 with a 58 cc head will yield about a 13:1 compression ratio. I think you will need to remove material from combustion chamber to get 10.2:1. I know I have to remove about 5 cc to get 9.3:1 with a 33 cc dish in piston. This 401 is for a pickup, should never hit 4000 rpm. Please explain the rod and rod angle benefit line in point two. I did a mock up of this and the rod angle to rod journal is definitely reduced using a 6 inch rod vs. a 5.7 inch rod. I would agree with your comment on piston manufacturer choice if this were a high rpm build. I do welcome and value the opinion of this forum in regards to parts selection and do rely heavily on technical advice of others. Afterall, there are those of you out there who have acturally done this and have the final results to share. Thanks.
Lets make sure I have right idea on compression ratio. Lets start with a 4.165 bore divided by 2 then squared then multiplied by the stroke. That would give the volume of the cylinder. I'll convert to cc early. Use 1 cubic inch equals 16.387064 cubic centimeters. Now we need stroke. 3.68 x 2.54 = 9.3472. Now bore x stroke gives 87.8997 x 9.3472 = 821.6. Now add the gasket and combustion chamber area, 9cc and 58cc to get total volume or 888. Now divide 888 by 9cc plus 58cc or 888 divided by 67 and we get 888/67 = 13.25:1. Consider the stock compression ration of 8.5 ish we get 888/8.5 = 104.47. 104.47-67=37.47cc for a stock piston dish.
If the the bore turns out at 4.195 and increase stroke to 3.817, the final cylinder volume is 862.407 cc. Add to this the stock 58cc for combustion chamber and 9 for head gasket we get 929.407. Divide this by 67 and we get a 13.7:1 compression ratio with a flat top piston. If I want a 9.3:1 compression ratio I need to cram 929.407 cc into a 99.93 cc combustion area. So 99.93cc minus some for head gasket thickness, (about 9 cc) minus 58 for the combustion chamber leaves about 33cc piston dish. Piston needs 33 cc dish to finish at 9.3:1 compression ratio providing you shave nothing from the head or remove material from stock combustion chamber. Any thoughts?
Elliott
03-14-2004, 04:08 PM
Please explain the rod and rod angle benefit line in point two.
Right, I should have said the benefit (other then less friction and stress on the piston skirt) is the torque at mid and upper end. Low end torque benefits more from a shorter rod, however the longer rod provides for longer piston dwell time at and near TDC. That means compression is held longer and combustion improves... all of which should be magnified by excellent flowing AMC heads and a Performer intake which promote increased air charge velocity to take advantage of the higher cylinder pressure after the first few degrees of rotation past TDC... before the pistons slow in their descent.
Someone correct me if I don't have this all straight...
On the rod size being 2.0", remember that them C*vy cranks were soft (like their blocks) so they probably needed larger journals on the bigger motors. On a forged crank (not that I'm a racer, just going by what they use) I don't think the 2.0" rod journal would be an issue or Indy Cylinder Head might not be running a 2.1" journal in the AMC Bracket Master 500 cranking 800hp - 670ft/lbs 7,400/4,500rpm at 14.0:1 compression. I do wonder if a little torque isn't sacrificed in reducing the reciprocation mass that close to the crank center line though.
I don't know about the ring pack and compression height issues, I'm still looking at which BB C*vy flat tops to use if I go with the 4.5 bore.
If you know of any web sites that layout the various piston dimensions let me know, where they list the pin center line to top of the piston, ring spacing, compression height, and all that. Kinda tough to find a place that has it all laid out complete.
Cheers
I have a .040 bored 401 block in the garage (a purchasing mistake, fortunately only cost $25). I think the bore center on the AMC block is 4.75 inch. I looked through the freeze plug hole and I don‚Äôt think the cylinder walls are much over .3 inch thick a few inches from below the top of the block. Actually, 4.75 ‚Äì 4.165 = .585. So each cylinder wall can't be over ¬? of that or .2925. I don‚Äôt see how you could bore a stock AMC block to accept a 4.5 inch piston. Even if you sleeved the block, each sleeve would only be .125 inch thick (4.75 ‚Äì 4.5 = .25. .25 divided by 2 = .125) The sleeves would have to touch all the way down to the bottom. I don‚Äôt see where there would be anything left to support the sleeve. Even if you hard filled the block, I think the torsional forces would twist the block past an acceptable limit. I‚Äôm not familiar with the Bracket Master 500, must be a very special ($$$$) block.
I also did further research into Wisco pistons, I found no case of failure due to material defect or workmanship at any rpm. If there is data out there please let me know where as I did not find it.
Elliott
03-15-2004, 07:21 PM
Not sure if the block must be filled to use those 4.5" liners... I've been trying to determine that. However on wet sleeve engines I've run the sleeves were only supported at the top and near the bottom. I haven't seen a sleeved 401 so I am still trying to find someone who's done it to advise me on it.
About the Wiseco pistons, I personally do not know much about them. Possibly what you haven't heard about them in auto engines is because they are new to auto production???
Here's a quoted from a guy who deals in off road toys that advised me against them, take it for what it's worth (ICH is the only place I've seen using 'em, they have a reputation at stake so....?):
"I wouldn't give $100 for a truckload of Wiseco pistons. I've been a Honda & Suzuki cycle technician for the past 25 years, and probably replaced a hundred broken Wiseco "racing" pistons before they sold their first automotive piston." Food for thought any way. 111!!!
Thanks for the insight. I'll research further. I had not delved into the cycle piston area for failure data. Based on what I can find so far, I conclude that Wisco has built a solid reputation in the automotive piston arena maintaining a record of reliability on par with Ross and others. But, as always, if some of you have input, I'm wide open.
Spent a little time the other day looking for bearings. Particularly the main bearings, the rod bearing will be easy because it will be a standard dimension sbc rod bearing. I was hoping to find a “performance” main bearing, not that I really need one considering the low rpm application. I looked into Federal-Mogal and Clevit.
I went to the Federal-Mogal web page,
http://www.federal-mogul.com/cda/content/front/0,2194,2442_897053_6752,00.html
Looking for an appropriate main bearing for the 401. Not finding exactly what I was after, I called the tech line, 1-800-325-8886 and talked with Gus. There is only one choice of bearing from Federal-Mogal for the 390/401 main, their standard copper/lead bearing pn 3311CPB and 3311CPA, four of one and one of the other, the middle main has a flange. I think these are their H-24 alloy. For the rod bearing, because I’m off-center grinding to accept a sbc rod, I can use the new tri-metal aluminum bearing. The new aluminum tri-metal bearing will outlast the copper lead bearing by a considerable margin.
Clevite also offers a 390/401 main bearing in their “P” series. Description is virtually identical to that of the Federal-Mogal. In Great Falls, MT a set of Clevite Mains will cost $66 - $78. Nearly identical to the Federal Mogals. I actually found the Clevites on the shelf for $67, .010, .020 or standard.
I surfed around a little and found this beb page.
http://homepage.mac.com/dgiessel/engine/hpvstq.html
I was looking for the torque formula. The main reason I wanted to add stroke to this build was to increase torque. An additional benefit is the improved combustion chamber gained from the custom Wisco piston and subsequent reshaping of the AMC combustion chamber. If curious, go to google and type in "calculating torque". You could spend all day reading.
Elliott
03-17-2004, 06:20 PM
How much torque are you lookin' to get?
The 401 builds torque real easy without any stroking or head modification. Increasing the head flow may even cost you on low end torque with this motor. Find the right cam grind and run 9.5:1 pistons with just a 4bbl and performer and you can get an easy 300hp/500ftlbs at 2,400rpm with stock exhaust and pump gas. If you're building for more torque then that.... I can see your interest in stroking it, but 500ftlbs is simply and relatively cheaply done.
jeepsr4ever
03-17-2004, 06:28 PM
powermonger?......LOL OK then we will have to do a writeup on a amc 427
Torque is King! 500ft/lbs and 300 hp at 2400 rpm would be fine. But I see this as a golden opportunity to get a little more. I do not intend to change the flow characteristics of the head, only the shape of the combustion chamber to bring the compression ratio down to about 9.3:1 and to improve the burn. I'm having a lot of fun doing this and along the way I hope others will follow along. I'd like to leave a parts list others can use to accomplish the same thing.
If you really want to get into the automotive math, check out the following web page.
http://www.martindalecenter.com/Calculators1_3_Auto.html#AUTO-MT and play around with some of the calculators. There are some very in-depth calculations on valve efficiency, airflow characteristics and much more, stuff way over my head.
I found the formula to calculate horsepower. Torque is a measurable commodity, horsepower is calculated. The formula goes like this:
hp = (Torque X rpm)/5252.101.
So if your engine is turning 2400 rpm and there is a measured 500 ft/lbs of torque, the hp is calculated at (500 X 2400)/5252.101 = 228.47 hp.. You’ll have to go look and see how the 5252.101 is derived. Just for gee wiz, in the 1800’s James Watt concluded the average horse could move 550 lbs in one second or 550 X 60 = 33,000 pounds one foot in one minute. Hence horsepower is the ability to move 33,000 lbs one foot in one minute, friction aside.
Elliott
03-20-2004, 09:40 AM
J20,
If you're shooting for more then 500ftlbs then you are on the right track with stroking and you should get there pretty easily I would think. I've read (and read only) that ~4.0" stroke is possible.
BTW, on the 300hp, 500ft/lb @ 2400rpm of that 401 I had built.... those were desktop dyno specs, I gave the printout to the guy who bought my Cherokee and can't reach him to get a copy back. Pretty sure that the 300hp was not at the same 2,400rpm and that it was just a peak figure, peak torque at 2,400rpm was my goal. I really wish I had the cam specs, but doubt the machinist would still have it after five years #-o
I am seriously considering spending some $ on a desktop dyno, seen the Dyno 2000 on EBay pretty cheap for like $20??? Does that sound right?
Also looking at the Performance Trends Engine Analyzer v3.2 and the v32plus.
Lifted79CJ7
03-20-2004, 08:30 PM
Elliott, talk to Fuzz about Desktop Dyno 2000. :wink:
Jack
PS-I am definitely following this thred. Keep up the work!! I want to see what kind of crazy torque numbers you get out of this thing! :lo1l:
There are several problems associated with a 4 inch stroke in a block with a deck height of only 9.208 inches. The rod to rod journal angles start to get large unless you are willing to sacrifice compression height, which will adversly affect the ring pack. Using a 3/16 top band and two standard dimension rings (1/8?) and an oil controil ring you need at least 1.1 inch. You could use a supported oil control ring but I believe a supported oil control ring adversly affects reliability. If you desire a race engine the rules change. If your after 100K miles of trouble free driving while building enough power to smoke the ch*vy, I think a 3.827 inch stroke (using the sbc 6 inch rod) should be the limit considering piston design and head work. If only the AMC engineers had increased the deck height to 9.5 or 9.6 inches when they decided the 390 needed grow some. If a 4 inch stroke was the goal, how would you get it? I think there are three options: 1) off-center grind the crank to accept a Honda size journal (1.8 - 1.85 inch) or some other rod with a 1.8 inch journal, 2) weld the crank up to increase the throw. I think a 1.8ish rod journal is too small for an engine developing such torque. Welding the crank to increase the throw is expecsive and 3) buy an after market crank, also very expensive. I think the biggest bang for the buck is off center grinding the crank (the cheapest of the above three) and I chose to use the sbc 6 inch rod because they are faily inexpensive. I welcome any other angles on this subject.
An integral part of this project is the camshaft. I put a lot of thought into exactly what I thought I needed. Unable to decide, I called the pros. I called Comp Cams (1-800-999-0853) and talked to Denis (sp). He asked me several questions: operating RPM (4000 or less), compression ratio (9.3:1), Vehicle type (J20 4X4 with manual 4 speed, future OD 5 speed), ring and pinion (3.73), tire size (33 X 9.50), cubic inch (425ish), other modifications (after market dual plane intake, custom pistons, small tube headers). After running the numbers through their software, Comp Cam's recommendation is the Extreme Energy 256H, XE256H. Denis said, considering the extra cubic inches, the XE256H would "feel" more like a 204 or 206 duration cam instead of the 212/218 duration stated for the 256H. He further stated, considering the application the XE256H would provide the performance increase (read that torque) I'm after without totally sacrificing fuel economy. It looks like we have winner. Have not ordered it yet, what say you?
Elliott
03-23-2004, 06:40 PM
I'm skeptical of salesman, any cam outfit is going to have "just what you need". That cam may actually work out perfect for your application, but I wouldn't buy it without running it's #s through a dyno first to see if it does to your torque curve just what you want. When I had my 401 built five years ago there weren't any box cams that would give me 500ftlbs at 2,400rpm with the mild build I was putting into it. That may have changed.
Maybe someone here has a file on that cam they can run for you with the addition of your other specs on the bore/stroke and run some comparisons. You might could do better with a custom grind. It's worth looking at in my opinion.
Elliott, thanks for the input. From the research I've done I think my cam profile will land somewhere between 206/206 and 218/218. Incidently, Edelbrock recommended their Performer RPM cam. I could look into a custom grind but for my low RPM application I'm not sure the additional expence would justify the minimal gain. Narrowing cam selection down to a basic category is the easy part, nailing down the exact duration desired is the hard part. I need a cam with enough intake duration and valve lift to ensure the cylinder gets a good charge with a high velocity finish (taking advantage of the dual plane intake) and enough exhaust duration with enough lift to ensure good evacuation. I Don't think I want to go over 220 on either one because to much overlap will adversly affect performance at low PRM (hence the higher duration = more overlap works better at high RPM which demands the single plane manifold). I think the recomendation from both cam companies are in line and almost identical. Note that both are above what would normally be used for a low RPM application but because of the additional cubes a little more cam is required but would feel like a cam of lesser duration. This is a very difficult area of engine build and open to much debate. I welcome all the data I can get.
In the above post, I made a mistake. Edelbrock recommended their Performer Cam, not their Performer RPM cam. That would be difficult as they don't make a Performer RPM for the AMC. My apologies. Also Crane cam lists an AMC V8 application at 204/216, .456/.484 for a 1500 to 4500 rpm range. The Summit 8600 goes to 214/224 with, which may be a little fast for my application. I think the Comp cam is a good choice. If anyone would like to run and post the computer generated dyno numbers for these grinds that would be way cool.
How much torque can I expect form the stroked 401? To help answer this question lets look at a proven, long standing model, the BBC. I did some looking into how much torque the BBC can make in the RPM range I intend my 401 to operate in (idle to 4000 RPM). I'll throw this out: the BBC will produce more torque than the AMC 401 given equal rpm, cam grind, fuel and aspiration because the BBC has a longer stroke and bigger bore. Should be no surprise, simple physics. I'll surmise the Ch*vey Performance center has done more research and spent more $$ than any American automotive company in developing automotive engines. I went through their list and found a close comparison, the 454 XETREME 4X4. Check it out at the following:
http://www.sallee-chevrolet.com/ChevyBigBlockV8s/454_xtreme_4x4.html
The dyno chart (actual dyno, not computer generated) states this engine will produce 462 ft/lbs of torque at 2400 rpm and tops out at 475 ft/lbs at 3500 rpm. The cam is a Comp Cam Xetreme Energy cam with a 206/212 and .510/.510 profile. Horsepower peaks at 316 @ 3500 rpm. I realize the compression ratio is only 8:1 on this engine. Raising compression ratio to 9:1 could increase torque and horsepower by as much as 4%. I believe if the Ch*vy engineers, utilizing their vast financial and technical resources, could have built a stronger engine while ensuring durability and affordability they would have.
Conclusion: 500 ft/lbs of torque at 2400 RPM from a normally aspirated, reasonably bored (say .060) AMC 401 running on pump gas is not a reasonable expectation even if it is stroked to 3.827 or even 4 inches regardless of camshaft selection. I think 400, maybe a little more, ft/lbs at 2400 RPM is more realistic. What say you? I welcome any comments or substantiated/documented counter arguments.
Elliott
03-25-2004, 01:38 PM
How much torque can I expect form the stroked 401?
Conclusion: 500 ft/lbs of torque at 2400 RPM from a normally aspirated, reasonably bored (say .060) AMC 401 running on pump gas is not a reasonable expectation even if it is stroked to 3.827 or even 4 inches regardless of camshaft selection. I think 400, maybe a little more, ft/lbs at 2400 RPM is more realistic. What say you? I welcome any comments or substantiated/documented counter arguments.
First off, I'm pretty sure you know more about what builds torque then I do. I've put some posts up here trying to learn some things that are AMC specific and I have some feelers out on other sites as well. I don't necessarily thing that the 454 is a good comparison for a few reasons, their heads just don't flow like an AMC head, and I believe the crank dimensions differ enough from the AMC that factors like smaller rod journals (and possibly lighter counter weights) might lead to less inertia/torque then the AMC crank. Also, Chevy uses an offset rod where AMC is not... and I don't know if that has any effect on torque in some way.
I'd be interested to see a good hard write up of comparison, haven't found much as of yet and don't personally have the experience (or parts) to put it together myself.
I'm pretty sure that MC here is planning to run some hard dyno tests on the 401 which should be revealing. The aspiration of a 401 is exceptional to start with and the addition of a 650-770cfm w/performer manifold will likely allow it to breath better then a stock '72 Pontiac 455 (that developed 300hp - 415ft/lbs 4,000/3,200rpm @8.2:1 comp.).... then up the compression to 9.5:1 on the 401..... and develop the perfect cam. I don't think 500ft/lbs is out of reach.
I know there are a lot of people that don't think much of desk top dyno #s, and apparently Tony Zamisch is one of them. However, I've had one AMC doubter run some #s for me on the Performance Trends software that his shop uses to build offshore race engines (at 900 hp their DT dyno comes in within 10hp of measured hp) and he was pretty impressed with how quickly the AMC builds torque compared to the big three. Like you, it would still be nice to see the actual curves run and hopefully we can look forward to some being put up here at Bulltear.
Elliott, I do appreciate your response. The data you speak of is exactly the kind of data that will rebuild (or re-announce) the once mighty reputation of the AMC 401. You are right on the dot with your comments about the superior airflow characteristics of the AMC dog-leg head design. I think the offset on the rod is no greater than .060. This can actually add torque as the offset is set to decrease the angle between rod and rod journal on the off-side travel decreasing the ever-changing force vector operating against downward travel or the force required to raise the piston. (the total force vector is a composite of the force vectors as the rod travels the circle, so when the crank throw is at 90 degrees to the rod the total force is only the downward vector. Past 90 degrees, the two will once again add to get the total force or add to get total force to raise piston). A very small gain. The offset also decreases the sideload on the cylinder wall. I, like you, do not have the resources to test various combinations and provide real torque data. I'll agree, the comparison of the AMC 401 to the BBC may not be perfect, but for the application it is close enough to draw conclusion. I'd love to get 500 ft/lbs at 2400 but I'm just not sure its possible. Please prove me wrong.
Elliott
03-25-2004, 08:46 PM
You have probably read the June '98 Hotrod article, they don't specify if the 500ft/lbs was an actual dyno reading:
http://www.javelinamx.com/JavHome/articles/hr0698-1.jpg
http://www.javelinamx.com/JavHome/articles/hr0698-2.jpg
http://www.javelinamx.com/JavHome/articles/hr0698-3.jpg
http://www.javelinamx.com/JavHome/articles/hr0698-4.jpg
http://www.javelinamx.com/JavHome/articles/hr0698-5.jpg
There is a good write up on the 360 estimating ~450ft/lbs:
http://amcforum2.tripod.com/rc_0788/360builduppage1.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage2.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage3.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage4.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage5.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage6.jpg
http://amcforum2.tripod.com/rc_0788/360builduppage7.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage8.jpeg
http://amcforum2.tripod.com/rc_0788/360builduppage9.jpg
Indy Cylinder Head's 407/401 is most likely tested on an actual dyno:
INDY AMC 401 (407ci) Bore x Stroke = 4.195 x 3.680 Bore to Stroke Ratio = 1.1399
Aluminum AMC 401 500hp - 480ft/lbs 6,300/4,500rpm 10.75:1 on pump gas.
Indy's heads supposedly don't flow all that much better then the 401 heads, and I don't think you really want them too for the low end torque. If this motor was cammed for low end torque and carbed vs injected I think you'd be a lil over 500ft/lbs. I've been trying to get more info from ICH, but they don't even have anymore catalogs and I have yet to receive the price list they promised me.
I agree with you that getting some hard dyno #s would be sweet.... but don't hold your breath for me to come up with them as I'm still building my shop at present. :wink:
Lifted79CJ7
03-25-2004, 09:40 PM
Hey Elliott, for some reason the second set of pages isn't coming up. Any suggestions? I've read the first article at home, but haven't seen the second. The only other true build up I've read on line is from www.jedi.com.
Later tatter,
Jack
I re-read the linked article, very impressive numbers. Thank you for posting it. The article states 508 ft/lbs at 5500 RPM. The cam spec is 274/282 at .050 108 degree lobe centers with unspecified lift. That is a lot of cam. I contend at 2400 RPM the torque is in the low 400 ft/lb range. If there is a cam out there capable of deliving 500 ft/lbs at 3500 - 4000 RPM, I sure would like to have one.
Elliott
03-26-2004, 09:26 PM
Hey Elliott, for some reason the second set of pages isn't coming up. Any suggestions? I've read the first article at home, but haven't seen the second. The only other true build up I've read on line is from www.jedi.com.
Later tatter,
Jack
Try this link and then click on the picture:
http://amcforum2.tripod.com/rc_0788/
Then here is the March 2004 HotRod 390 article:
http://www.gremlinized.net/images/articles/hotrod390p1.jpg
http://www.gremlinized.net/images/articles/hotrod390p2.jpg
http://www.gremlinized.net/images/articles/hotrod390p3.jpg
http://www.gremlinized.net/images/articles/hotrod390p4.jpg
http://www.gremlinized.net/images/articles/hotrod390p5.jpg
Lifted79CJ7
03-27-2004, 04:17 PM
Sweet, thanks for the hook up Elliott! :?
Elliott
03-28-2004, 10:43 AM
I'm having the crank of my 401 off center ground to accept a 2.1 inch sbc 6 in rod, should get about 3.817 inch stroke. Plan to use a Wisco piston, anyone else tried this? Will have to remove about 4 - 6 cc from combustion chamber to keep compression ratio down to 9.3:1. Any thoughts?
On the rod/stroke ratio I found a place to calculate your rod angle at:
http://victorylibrary.com/mopar/rod-tech-c.htm
(they also give a pretty good analysis of various angles)
Your "N" value would be 1.5719151
-so-
.5/1.5719151= 0.3180833 Inv sin= 18.6 degrees, which compares to 18.3 for the stock 401. From what I read there the 401 runs pretty steep in stock form.
Elliott "you da man"! Thanks for that link. The link you provided gives meaning to the answer, meaning I did not have. I had calculated the connecting rod angle at 18.54 degrees. Imagine a triangle with the 90 degree angle centered on the crankshaft main journal, the next vertices centered on the connecting rod journal and the third vertices centered on the piston pin. Divide the stroke by two and this is the distance between the center of the main journal and the center of the rod journal when crank has rotated 90 degrees past TDC. The rod length is the hypotenuse. The second side, which we really don't need (the bore), is calculated using Pythagorean’s theorem. Stroke divided by two, 3.817/2 = 1.9082. 1.9085 squared is 3.6424. Hypotenuse squared is 6 squared = 36. So 36 - 3.6424 = 32.3576. take the square root of 32.3576 and you get 5.6884. Now the sin of an angle is opposite over hypotenuse, or 1.9085/6 = .31808. Do the inverse sin thing and the angle comes out at 18.547 degrees. Could use cosine to get same answer (adjacent over hypotenuse 5.6884/6 and get the same 18.547 degrees) What Elliott's link has provided is extremely important to all off us considering engine geometry modification. The link identifies an optimum (at least an opinionated optimum) rod to stroke ratio of 1.7:1 and a rod angle guild. Considering this build, with a rod to stroke ratio (n) of only 1.5719 and a rod angle of 18.547 degrees, I am on the edge. Don't these numbers look a lot the BBC numbers?
Elliott
04-10-2004, 12:00 PM
Here's a another calculator you might could use:
http://www.rbracing-rsr.com/squishcalc1.html
Briteblock
04-10-2004, 01:03 PM
5 pages and nobody has turned a wrench? :shock: Lets see some pics MC.......huh huh?
:mrgreen:
You’re right, five pages and nobody has turned a wrench. I walk past my pile of parts everyday and wish I could assemble something. The hang up is I don’t have a piston yet. The block needs bored to determine the final size. The machinist can’t get the block into his schedule for another few weeks. Point of interest. Mad Dog Racing has cut a deal with Ross Pistons for a screaming deal on forged AMC pistons, about $575. Check out their web site. These pistons will work as stock replacements for serious builds. They won’t work for my stroked application. DW is working several AMC specific projects. When I do get pistons, I’ll be sure to take pictures of piston to show difference is shape and of head to show how it was opened up. Wish I could offer more.
jeepsr4ever
04-10-2004, 11:45 PM
575 for ross pistons.... sounds like just over cost for mad dog...not quite sure about those guys (guy)
Lifted79CJ7
04-11-2004, 08:00 PM
So is that for 401 pistons I take it? So far I haven't heard too much about Mad Dog. Only time will tell. They seem to have a lot of positive feedback on ebay, though. Now to just find $600 somewhere......
Good news;
The block bored at 4.190. I will use a standard sb Ch#vy ring pack with a vortec style combustion chamber. I ordered a set of Manley steel H-beam 6 inch sb Ch#vy connecting rods (2.1 inch journal) today from CNC Motorsports. Lowest price I could find on Manley rods. I was going to use Eagle but they are not forged in the USA, Manley is. I also ordered a set of guide plates from Performance American Style. I should have a set of custom Wisco pistons in a few weeks. On a side note, the complete 401 engine I purchased for $30 had according to the owner 178,000 miles on it. It had spun the #1 rod bearing and had a broken piston skirt on #6. The block would have bored at only .015 over! Good steel in those AMC blocks! More follow.
Elliott
05-01-2004, 05:48 AM
Any plans of running a dyno on this when complete?
Have you got any pics of the combustion chamber to post?
Dusty
06-07-2004, 02:20 PM
Any updates.
I know there is an engine dyno in Greatfalls, my friend Verlin From missoula used to run up there to test and tune his motors for running at Anaconda Lost creek racetrack.
:lo1l:
Lifted79CJ7
06-07-2004, 08:39 PM
I'm with Dusty!! You got us all worked up, then nuthin'!! I can't wait to see this engine..... :? :t: :lo1l:
Jack
Sorry for the delay. Still no pistons. I've been working with Performance American Style for a custom ground Crane hydraulic roller cam shaft. (went with a custom ground Crane hydraulic roller cam) Elliot got me thinking about a custom grind. ( Ordered the Edelbrock Pro Flo EFI from Bulltear 3 Jan 2005). Then a NV4500. That should about do it. Should produce enough torque to move the J20 down the road.
Dusty
06-09-2004, 08:41 AM
Have you built your NV4500, if not i would SERIOUSLY consider chasing down the Fully splined OD outputshaft for diesels and V-10s but depending on the t-case you be scouting fot the right input gear, your going to have more torque than a V-10 and V-10's have problems rattling OD off of the stock shaft occasionally. The full splined output shaft is $150 or you can ussually find a rebuilt tranny with the upgraded shaft, also look to a Dodge tranny it might be your best friend, but that depends on the t-case you intend to run.
Dusty, Thanks for the data on the NV 4500 output shaft. I got basic cam specs today. They are as follows: Crane hydraulic roller for .050 .458 Intake lift @ 204 duration. .462 Exhaust lift @ 214 duration. Good for off-idle to 4500 rpm, cruise at 1900 - 2400. Exactly where I want to be. Roller will allow very fast valve action allowing higher mixture velocity, allowing a denser cylinder pack - equal to one or two ounces of boost?
Your cam sounds very similar to the Crane 260 I'm going to be using. The following are DD2K results that you may find interesting for comparison. The TQ ###s should make me very happy.
401 w/ stock bore, stroke and heads, 9.5:1 comp, air gap dual
plane intake, 650 cfm TBI, and small tube headers. Crane 260-2 cam (456/484 lift, 204/216 duration, 112 LCA).
>Here's what DD2K says:
>
>Crane HMV-260-2
>
>RPM HP TQ
>2000 173 454
>2500 219 459
>3000 266 466
>3500 303 455
>4000 342 449
>4500 322 375
>5000 315 331
>5500 296 282
>6000 260 227
Just a side note: The formula I posted earlier for calculating HP is working according to DD2K.
2000 173 454
>2500 219 459 = (2500x459)/5252.101 = 218.48
>3000 266 466
>3500 303 455
>4000 342 449
>4500 322 375 = (4500x375)/5252.101 = 321.29
>5000 315 331
>5500 296 282
>6000 260 227
Remeber, torque is measured, HP is calculated. Pretty cool :lo1l:
Good news! Custom Engine and Machine (the machine shop doing the machine work here in Great Falls, MT) called today and stated the pistons and rings are in. Mike also finished off-center grinding the crank to a final 3.820 stroke. I'll post the exact piston specs from the build sheet in a day or two. Custom ground Crane hydraulic roller cam and matching lifters should be here in two weeks. I ordered the cam through Performance American Style, a very professional outfit. Took the time to work up exactly what I wanted and bested Summit Racing's price for cam and lifters by about $90. Stand by for piston specs.
I’m providing this data in an effort to make it easier for anyone else who wants to do a similar build. Keep in mind there is head work involved, you have to remove about 5cc from each combustion chamber, if you decide to use this stroke (3.820), bore (4.190) and piston combination.
Wiseco Piston Inc. built the pistons (they are beautiful). Job Number 8622, piston forging F6369ZA. Bore size is 4.190 @ a suggested clearance of .0040. Compression height is 1.275. Wrist pin S451, pin diameter .927 (sbc) pin length 2.950. Ring type 1/16, 1/16, 3/16. I think the ring land and grove width and grove root diameter match a sbc 400 bored .060 over. The piston has a .206 dish measuring 33 cm cubed. Intake valve pocket diameter is 2.2 at 18 degrees and exhaust is 1.8 at 18 degrees. The pistons are closely weight matched at 466.6 – 468.4 grams. Pistons came with a matching set of very nice rings.
Lets add up the numbers. AMC theoretical deck height is 9.208, center line of crank to top of cylinder. Started with a 3.68 stroke and a theoretical 2.247 inch rod journal. Off-center ground the crank rod journal to 2.1 gaining .147 inch of stroke. 3.68 + .147 = 3.827. Mine came in at 3.820. So, center of rod journal at bottom of stroke to top of cylinder is 9.208 + (3.820/2, because half the stroke is above center line of crank and half below centerline of crank) = 11.118. Now, Stroke + rod length + compression height is 3.82+ 6.00 + 1.275 = 11.102. 11.118 - 11.102 leaves about .016 when piston is at TDC. I know the numbers on paper may/will not match what I get when assembled which is what I get to do next. I get to put it all together and make sure it all fits. I also get to make sure there is at least .060 clearance between connecting rod and bottom of cylinder and camshaft. Waiting on camshaft. Should have ordered it earlier. Then the rotating assembly - crank, rods, piston, balancer, flywheel and pulley - gets ballanced. Mill the timing gear for camshaft keeper (a must with the roller cam, prevents cam walk), do the valley oil mod and I should have a completed short block.
Mudrat
07-09-2004, 04:46 PM
WOOOF!!!!! I want to see pics and hear an audio clip when that bad boy lights off!!!
What does Dyno PC think your going to get for HP and TQ??
Good luck!!
Mudrat
hohner0006
07-14-2004, 09:19 PM
I am interested in doing this to my 401 but i'm looking for 600+ HP at higher RPM's for drag racing in the mud. I want to go up a class but I'll be competing with 750 - 850 HP F*rds, D*dges & Ch*vies. I will use my cj7 through a t400, 3,000 stall, D20, 4:56 gears, MSD dizzy and 6T box w/rev limiter, Predator carb, dual plane intake, ported heads and run 13 x 37 x 15 Boggers. My biggest hurdle is that I must pull 15" of vaccuum at 800 rpm. I know I'll have a 1,500+ weight advantage on the fullsize guys so I won't need as much HP. A lot of what you guys are discussing seems more for low rpm torque not high rpm HP. What suggestions would you give me on my build-up? Thanks, Hohner0006(I'd post a pic of my cj if i could figure out how!)
My goals/objectives for this build was to significantly best the performance of the ch*vy HT383’s 435 ft-lbs torque at 3500 rpm and 340 hp at 4500 rpm. One sure way to accomplish this is to utilize a stroke longer than 3.75 inches and a bore bigger than 4.030 as there is no substitution for cubic inches given normal aspiration. DD2K says I’ll best the HT383 numbers with no trouble. Had I needed/desired more than 500 ft-lbs of torque or more than 600 hp at any given rpm I would have selected the ch*vy big block. At the risk of offending all, I do not believe the AMC V-8 is a suitable platform for more than 600 hp given normal aspiration and pump gas (especially if you have to maintain 15” inches of vacuum at 800 rpm. That is a very severe cam limitation). I say this because the deck height is simply not tall enough at only 9.208 inches to reliably/realistically fit more than a 3.9 inch stroke while keeping the piston pin out of the oil control ring and with a 4.75 inch bore center the AMC V-8 block is limited to about a 4.25 bore. Given these limitations the maximum cube is about 442 and that is way out there on the edge. An AMC block so configured will not live long because the cylinder walls would be so thin and rod angle too great (A few pages back we listed calculations for my rod angle at 18.6 degrees. Seventeen degrees is the established optimum and over 19 degrees creates exponentially increasing amounts of side-load force). To further justify my position, lets look at a few built examples. The ZZ502 delivers 502 hp at 5200 and 567 ft-lb of torque at 4200 rpm. This is a middle of the road build utilizing a 224/234 hydraulic roller cam and 850 cfm carb and produces about 1 hp per cube at peak and a little over 1 ft-lb of torque per cube a peak. The world power 509 cubic inch Merlin big block ch*vy will produce 540 hp at 5500 rpm, more aggressive 236/246 hydraulic roller cam produces about 1.06 hp per cubic inch displaced. Lets look at the Huntsville 406 ch*vy smb all-out racing motor. Produces 575 hp and 431 ft-lbs of torque at 7000 rpm, 12.9:1 compression (pump gas is out) with Demon 750 cfm double pumper and produces 1.42 hp per cubic inch displacement (15” of vacuum at 800 rpm, I don’t think this engine will run at 800 rmp). Also note the cost per hp goes from $14 per horse ($7,460) for the ZZ502 to $19.65 per horse ($11,300) for the Huntsville 406. Engines running at 13,000+ rpms are very doable but very expensive.
Back to our beloved AMC V-8 before I get inundated with hate mail. If we limit the stroke to 3.82, keeping the piston pin out of the oil control ring, and bore to a more reasonable .060 over 4.225 we will end with 428 cubic inches. If be build for an aggressive 1.5 hp per cubic inch displaced (I’ll give an advantage to the AMC heads and increase the ratio above the Huntsville’s 1.42 hp per cube example) we have the potential for a theoretical 642 hp. BUT we are not running on pump gas as our compression ratio is at least 12.9:1 and I don’t think 15” of vacuum at 800 rpm is possible given the very aggressive cam we would have to use. If we devalue the hp by 12% for a 10:1 compression ratio we end with 564 hp, well below 600 hp. If we add a supercharger…., the rules change. I believe if your looking for more than 600 hp in a normally aspirated, reliable, stay together for more than a few runs down the strip AMC V-8 - you won’t find it. You’ll be better served with a big block ch*vy. Okay – hit me.
jeepsr4ever
07-15-2004, 02:39 PM
That is a interesting point but lets not forget about extra's like block filler. We have a guy here in town runs a 870hp 401 (not sure on overbore) with a supercharger and block filler up to the edges of the water ports. He runs cool all day! And its reliable!
Its true the blocks can only handle soo much for soo long, they arent 1000hp blocks BUT they can handle alot and cubic inch per horsepower is incredible with these engines. I do understand what your saying. a 426-426-428-436-438-500-523-528 cubic inch AMC can and has happened with great results
hohner0006
07-15-2004, 02:39 PM
I appreciate your honesty and bluntness. In the long run , it saves me a lot of time and money! I thought since 406 ch*vies run so damn hard at the track, the same potential would apply towards the 401 AMC. (Just at a higher cost) You seem VERY knowledgeable, so expain how even a bbc or bbf can make 850 dynoed HP and still pull the 15" of vaccuum? Obviously the cubic inches helps but , like you said, the cam limits your full potential. By the way, you are allowed any race fuel except alcohol or nitro blend. Most are running 114 octane but 1 is running 116 vp fuel.
Based on your views of the AMC engine, tell me what you feel I could build for a reliable go fast engine and at what hp range it would take to move a 3,000# jeep 150' quickly. At least quickly enough to run with the 5,000# + big hp trucks. It will give me something to shoot for or reach a decision to abort the whole project. Thanks, Hohner
You are undoubtedly correct about the many possible methods of obtaining more than 600 hp from the AMC V-8 if you use some or a combination of the following: supercharger, special high octane fuel, non-street typical compression ratios, stroker crank (I think you can buy up to a 4.135 inch crank for the AMC), highly modified heads/intake manifold or a very radical camshaft and are willing to accept the significantly increased cost and significantly reduced engine life that will come with some of these combos. You do raise a valid point I failed to consider as my focus is primarily on a 100K+ mile build. You open the door for numerous very potent prospects. Lets consider the supercharged 870 dynoed hp example. Lets say a GM 870 blower is employed and adds a healthy 8 lbs of boost. This will increase fuel/air charge in cylinder about, depending on barometric reading, (8/14.7 = .544217) 54% with subsequent proportional gains in horsepower. Given this scenario, I believe a supercharged 401 can easily hit the 870 hp mark, normally aspirated at 550 hp + 54% + high octane fuel = 870 hp (I realize there is not a 1:1 correspondence between % boost and % hp). Keeping it cool under a continuous 870 hp load will prove very difficult. A 523 cubic AMC block is possible if a 4.135-inch stroke and 4.50 bore is utilized. This combo can be done with a stock 5.85 inch rod connecting rod, a reasonable compression height (maybe a little short with a compressed ring pack) but the cylinder wall finishes at only .25 inch, block filler a must. Rod angle will be over 19 degrees, 20.69 degrees. Stroke divided by 2 then divided by rod length is 4.135/2 is 2.0675/5.85 = .3534, inv sin = 20.69 degrees. A little to much for my comfort. Could use a longer rod and sacrifice ring pack. Hohner, I’ll bet this really has you confused. I would appreciate (read this as need) the opinions of others who are running high horse AMC V-8s. Thanks.
Mudrat
07-15-2004, 05:20 PM
(I'd post a pic of my cj if i could figure out how!)
I'll let the big block techeeeeeess handle the HP side. To post pics, you need to have them somewhere that you can link to. Either your own website/address or an image host. A lot of us use Webshots, (http://www.webshots.com/homepage.html) or Ripway (www.ripway.com)
What you need to do is while you are writing your post, use the buttons at the top of the posting block. You'll see them listed from B for BOLD to [URL].
To show a picture the format would be ** web address with NO spaces between the start and finish [img] blocks. To show a link like I did use text ( the link). You can also change text color and style the same way.
More questions, just ask.
Mudrat
Mudrat
This is all very interesting, but why do you want to use the 401? I would think it would be much cheeper and easier to run a BB in your jeep and be competitive (I would have thought an auto would be a better tranny choice too). Also I don't think your dana44s will hold up to that kind of power.
hohner0006
07-16-2004, 07:03 AM
To run the CJ I have to run corporate matching motor trans & trasfer case combo. This is what I like about Jeep/AMC, it lets me run my choice of a t400, tf727 or AMC 999. Also, D20, D300, 208 t-cases. BUT I have to run the AMC engine. IF I built up my J4000 (title weight at 5,350#) I would then have the engine choice from the Buick side of GM since 350 buicks were used in production. (I already got a ruling from the Race board that denied me the use of any other GM engine line other than Buick in the p/up and a denial to apply this engine into my CJ since none ever left the factory with one in the engine bay.) My next choice could be the XJ series that had the POS GM 2.8 v-6 in it. I can put a potent 406 stroker or BB in it but their design involving no real frame (uni-body) could lead to structural problems even with a full cage with a high HP SB or BB. If I have to go through this much work I might as well buy a paddle car and not worry about any rules at all. Look up www.southdakotamudracers.com under "classes" at the Super Stock rules as this is my guideline for building up my cj.
So maybe you can see why I want/have to build a potent 401 for my cj. I want the flexibility in my driveline choices and the lighter weight. I know my D44 may be my weak link but I can always put moser or MW axles in it or go to the D60 (add 350+#). I just need to get the engine buildup decided so I can get started on it first. The rest I can get done during the off-season.
Another key consideration for Hohner, in your desire to go 150 feet quickly is that the longer you make the stroke the longer it will take to get the engine to what ever operating rpm delivers max hp. A shorter stroked large bore engine will rev very quickly and develop hp very fast at the expense of torque. (shorter leverage arm/faster motion). The big block crowd simple overcomes this obstacle with sheer brute force via additional cubes. Your gains will have to come via superior volume metric efficiency and gearing as the AMC V-8 is simply not cable of the cubic inch displacement of the big block given 4.75 bore center and a 9.208 deck height. The ch*vy big block has a 9.8 inch deck height and greater bore center. I would recommend to you that you focus less on actual hp and focus on your hp to weight ratio and line up the hp/torque curve with your gear ratios. You have a significant weight advantage, you say 1500 lbs? If so, you can achieve the same results with 600 hp as the bigger rigs can achieve with 850 hp. Your lighter vehicle with quicker to accelerate engine and proper gearing should prove a winning combination.
My recommendation. Use your 401, off-center grind crank - stroke to 3.82, use a good ch*vy 6 inch steel h beam connecting rod, get some good pistons with high compression ratio, open up the heads (Edelbrock AMC performer heads?), have an aggressive cam custom ground (roller or otherwise, Performance American Style can/will help), consider fuel injection, do whatever oil modifications you see fit (consider the Miladon (sp) dual feed system? There are members on this list very qualified to talk to this). Build to operate at 7500 rpm and kick ASS! :lo1l:
Elliott
07-17-2004, 01:37 PM
Okay – hit me.
A nitrous fed 700hp 401 has been running reliably enough for Dave Allen in his race Cherokee ( http://www.daveallenracing.com ), reliably enough that he built a 2nd for his CJ. GM blocks are soft compared to the 401, there is a reason they need 4 bolt mains. If big HP wasn't possible, reliably, of the AMC then I don't think Herman Lewis would have much of a reputation and I don't think ICH would have built the aluminum block for 800+hp on the very same cylinder centers with short compression height pistons.
MC ran some auto cad on the stock 401 block and it sure looks like it could be reliably wet sleeved for 4.374" liners to match up with a 4.15 Moldex crank that ICH uses in the tall deck height aluminum AMC 500ci.
Now, I'm not much on math, but I am a betting man and regardless of rod angle crap I've read about (that seems to be largely ignored by ICH among others, ICH Bracket Master 500 runs 19.55* with only 0.192"s more deck height and 6.2" rods) I'd say a fire breathing 500CI could be built on the 401 core with 6" rods that would pump out over 600ft/lbs easily without race fuel even, much less gas or a super charger.
The AMC block has the same cylinder centers that the Mopar 440 has, how far do they get built? Taller deck height, granted.
The stock 401 has a rod angle of 18.30*, with 4.15" throw on a 6" rod for the 500 CI you'd have about 20.20*, only slightly steeper then the Bracket Master. Yes, you'd likely need a oil support rail 1.120-1.238"CH piston, but they run those in stroker Mopars... and the Bracket Master 500.
I'm not sure that +.65* of rod angle is anything to sneeze about even with a short compression height piston if you only need 10:1 compression to turn 650+ ft/lbs on pump gas. A 200,000 mi street motor, probably not... but who seriously builds a performance motor to last 200,000 miles? :idea: Just my .02 and I haven't built any 401 that even desktop dynoed over 500ft/lbs for 5-6 years. You have enough nickle in that AMC block to throw what ever you want at it in my opinion. I wouldn't hesitate to put it up against any big block out there.
Elliot, glad you wrote, what took so long? If your building a long life motor you need to consider rod angle because the ovalating forces exerted on the rod mains will literally tear the rod main apart if the rod angle is too great as rpm increases over 4500, I think 19 degrees is the limit for a long life motor (over 100K miles). Forged steel rods, balanced and blueprinted components are a must for applications exceeding 19 degrees and 4500 rpm. As for the high nickel content of the AMC block, it is not that much higher than others, try a punch test and you’ll find little difference. A trip to your local machine shop will reveal little difference in the machining or hardness characteristics of the AMC block vs. others. The Mopar 440 is a strong motor but there is a reason it is no longer is production or a first choice race application engine – it simply does not have the endurance or reliability of others (I'll catch H*ll for that one). Having said all that, I do not dispute the ability of those (and they are much more knowledgeable than I) who get upwards of 450 cubes and over 600 hp from the AMC platform. My point is that the AMC block, from an engineering/construction standpoint better correlates with the small block ch*vy than the big block ch*vy and we can’t realistically ever expect to exceed the potential capability of the ch*vy big block. We can however easily exceed the potential capability of the ch*vy small block.
I will concede that what I am building and the builds Elliot speaks of are vastly different. If the big block ch*vy crowd applied the same proportional gains they would hit the 600 cube mark and generate 200 hp more (at a minimum) than the 500 cubic inch AMC. See my point? To achieve big block ch*vy performance levels the AMC user must push the platform to greater extremes, greater extremes increase the probability of failure given the same conditions. If you are willing to accept those increased risks, by/buy all means build away.
Elliott
07-17-2004, 10:30 PM
Isn't the steeper rod angle part of what helps the 401 build torque faster per comparable level of build then other small blocks? Obviously there is a point of diminishioning return. I ran a lot of comparisons trying to figure out why the Caddy 500 is such a relative dog and I think it's much more then just the heads, I think it boils down to rod angle, possibly lighter crankshaft counter weights and stroke? What I mean (and this is a dis on big blocks :wink: ) if you took a bone stock 401 and simply added 99cubic inches to it and nothing else, compared actual net hp and torque the AMC would walk away hands down.
I know, I know, I should run my motor instead of my mouth... so I'll keep this short until I have the income to put my plans to work. I've never put even 100,000 miles on any vehicle or engine I've ever owned so if I get that out of a 500CI AMC whether I build it or use an ICH block I'm sure I'll get my moneys worth of smiles out of it.
For the moment I have to focus on getting my shop built, but I enjoy reading about your build and look forward to the dyno results... gotta feeling you will be quite pleased. :mrgreen:
Now as far as proportional gains, if you took a GM 400 and threw a hundred cubes at it you'd still have a POS. For what you get in a big block 500 it's really comparably pathetic if you look at net hp and were to use the same compression ratios as the 401. For the extra 99 cubes in the caddy, the BEST net hp rating with higher compression pistons only made 120ft/lbs torque over the 8.3:1 mildly cammed Jeep 401. If you could throw another 100 cubes at the Caddy I don't think the block could take it (it darn sure won't rev to 7,500) and you sure wouldn't get the proportional increase in torque that you can obtain from a 401. Running pump gas I just don't think you can double a Caddy's torque by adding 100 cubes, or any other big block for that matter. Sure you can ultimately build more power in a big block, but not so sweetly as the AMC. Does make me kind of wonder what you might end up with if you threw 100 cubes and the ICH Bracket Master 500 though! (Although I don't think you could.)
so much for short...
Block hardness? There must be enough of a difference if the AMC crowd will race with 7-800hp on two bolt mains. Doubt there are any 4bolt main big block lovers out there running hp like that who would take two bolts out of each main cap and have the same confidence in their block. Program has 4 bolt mains for the 401, Miloden used to.... but does anyone need them... or even buy them? Maybe you would want them for 1000hp, but would a GM 4bolt small block even handle that much HP?
AMC, as a small block... just flat rules :t:
jeepsr4ever
07-18-2004, 12:14 AM
here is a little to add to the fire
Edelbrock insider told me this.
They have on a Dyno a 480hp 401 here are the specs
401 stock bore stock crank stock pistons
Edelbrock heads, EFI, (special NEW camshaft) headers.
:!:
I magine with a bump in stroke and compression
Oh and as far as rod throw and angle are considered, you guys are close to understanding the mystery of why AMC V8's (of larger displacement) are power mongers :idea: devils in the details men :wink:
I have tremendous respect for those Edelbrock engineers. I'll go a little further out on my stressed and already cracking limb and surmise the Edlebrock engineers have concluded the optimal stroke for the AMC V-8 is somewhat less than 4 inches (3.9ish) and with max bore (.060) will finish at about 440 cubic inches. (What if connecting rods with offset rod journals where used like those in some of the bigger inline engines?expensive!). I'll further surmise Edelbrock has already done the dyno on the 440 cubic inch option with a 250 to 260 (I may be a tad, 5-10, low on cam spec) duration roller cam, 10:1 compression ratio, Edelbrock Pro Flo EFI, Edelbrock Performer RPM heads and got 600 - 650 hp at about 6500 rpm. How close am I?
I'm not sure where the extra (I’) and others came from. I do know my previous message took forever to post.
jeepsr4ever
07-18-2004, 09:30 AM
:-|
Okay, here is the MATH. The following tables contain theoretical calculations for rod angle, compression height, compression ratios, piston dish depth/volume and a compression height minus a ring pack thickness of .4375 minus ¬? of a .927 (.4645) pin diameter. These numbers are approximations as I do not have exact piston manufacture's dish rim thickness or ring pack dimensions (I approximated it at .4375 and .25 inches). I also did not include any room for bearing clearance or head gasket thickness because there is a lot of difference(.003 - .006 and .025 - .060). Again this is simply a guide. You will note the negative values for the dimension between piston pin and bottom of ring pack as stroke goes over 4 inches in the 9.3:1 compression ratio case and over 4.135 in the 13:1 compression ratio case. What that means is there is no more metal, you hit the wall! Look closely at the 3.92 inch stroke, 9.3:1 compression ratio utilizing a 6.125 inch rod with a 18.66 degree rod angle - there is .004 material above the piston pin. That is why I consider the 3.92 inch stroke the maximum for the 401 at a street level compression ratio keeping the oil ring out of the piston pin. I chose the 3.82 with a 6 inch rod and 18.66 degree rod angle with a compression height sufficient enough to leave some metal above the piston pin. Again these numbers are simply a theoretical guide. Your exact build will vary up to maybe .100.
stroke.....stroke/2.......Rod........Rod Angle....Comp.....Cylinder..Final
...............................Length............. ...........Height....Volume...Volume
3.68...........1.85..........5.85.........18.33... .....1.52.........51.593.......412.74
3.82...........1.91..........6.00..........18.56.. ......1.30.........53.556.......428.45
3.92...........1.96..........6.00..........19.06.. ......1.25.........54.958.......439.66
3.92...........1.96..........6.125........18.66... .....1.12.........54.958.......439.66
4.00...........2.00..........6.125........19.05... .....1.08.........56.079.......448.63
4.00...........2.00..........6.135........19.02... .....1.07.........56.079.......448.63
4.135.........2.0675......6.25..........19.31..... ...0.89.........57.972.......463.78
4.135.........2.0675......6.35..........19.00..... ..0.79.........57.972.......463.78
4.25...........2.125........6.35..........19.55... .....0.73.........59.584.......476.67
4.35...........2.175........6.535........19.44.... ....0.50.........60.986.......487.89
Stroke....Piston Dish...Apprx.......Piston........Comp Height
..............at 9.3:1.......Dish..........Dish.........- Ring Pack
..............Cubic In......Depth........Cubic CC..- Dish Depth
.................................................. ..............- 1/2 Pin Dia
3.68........2.009..........0.184.........32.92.... ....0.433
3.82........2.220..........0.204.........36.37.... ....0.193
3.92........2.370..........0.218.........38.84.... ....0.129
3.92........2.370..........0.218.........38.84.... ....0.004
4.00........2.491..........0.229.........40.82.... ...-0.047
4.00........2.491..........0.229.........40.82.... ...-0.057
4.135......2.695..........0.247.........44.16..... ...-0.258
4.135......2.695..........0.247.........44.16..... ...-0.358
4.25........2.868..........0.263.........47.00.... ....-0.431
4.35........3.019..........0.277.........49.47.... ....-0.680
Stroke......Piston........Apprx........Piston..... ..Comp Heigth
................Dish at......Dish..........Dish..........- Ring Pack
................13:1..........Depth.......Cubic CC...- Dish Depth
................Cubic In.....................................- 1/2 Pin Dia
3.68..........1.44..........0.132........23.547... ....0.511
3.82..........1.59..........0.146........26.021... ....0.277
3.92..........1.70..........0.156........27.789... ....0.217
3.92..........1.70..........0.156........27.789... ....0.092
4.00..........1.78..........0.164........29.202... ....0.044
4.00..........1.78..........0.164........29.202... ....0.034
4.135........1.93..........0.177........31.588.... ..-0.161
4.135........1.93..........0.177........31.588.... ..-0.261
4.25..........2.05..........0.188........33.621... ...-0.330
4.35..........2.16..........0.198........35.388... ...-0.575
See the negative numbers? That means you can't do that. You can use a one ring ring pack but that is no good in a daily driver. Again this is a theoretical guide for an AMC block at .060 bore. This does not take into account the posibility of sleeving the block to a bigger (over 4.225) bore. If you increase the bore over 4.225 and keep the dish the same your compression will change. You'll have to recalculate to see if the compression goes up or down. Your actual results will vary some but not much. What say you?
Bummer - the headers did not line up. Makes it hard to read but it is possible. Also, I don't know where the extra ’ stuff is coming from. Sorry.
Custom hydraulic roller cam showed today in mail from Performance American Sytle. The specs are as follows: Crane Part No. 86HR00004
Grind Number HR-204/286-2-16. Lift Intake @ cam 286 @ valve .458. Lift exhaust @ cam 301 @ valve .482 both with 1.6 rockers. Intake opens at 17 deg BTDC and closes at 63 deg ABDC with advertised duration is 260. Exhaust valve opens at 74 deg BBDC and closes at 16 deg ATDC with advertised duration of 270. Spring requirements are dual at 120 lbs closed @ 1.875 and open at 296 lbs @ 1.1415. Part number on springs is 99893. Cam Timing @ .050 intake opens at 9 deg ATDC closes at 33 deg ABDC max lift at 111 deg ATDC, 204 duration. Exhaust opens at 48 deg BBDC closes at 14 deg BTCD max lift 121 deg BTDC with duration of 214 deg.
20 May 2005. The valve springs Crane said will work will not work. The problem is the installed height of 1 7/8 inches is not obtainable with stock length valves, retainers and keepers, only gives about 60lbs of closing force, installed height is .1 too short. So, now that the stock valve won't work, the new plan is to use a bigger intake and exhaust valve, .208 and .176. This should get even better as we can make the engine behave as if there where .5 inch lift instead of .458/.482. More to follow.
That goofed up chart realy bothers me. How do you post an excel spread sheet? I added the dots, looks much better.
Mudrat
07-20-2004, 08:39 PM
That goofed up chart realy bothers me. How do you post an excel spread sheet?
You can't - I've tried all sorts of things. Its the text code the forum software uses. If you put in more than 1 or 2 spaces the software concatenates the string so it's only a single space.
The only way you could 'make it look (sorta) right' is to use a bunch of ...........
Sorry dude, wish we could, it would make life easier :roll:
Mudrat :oops:
Elliott
07-21-2004, 07:15 PM
I don't know, I'm not much on the math... but by what I interpret from your table (correct me if I'm wrong, it wouldn't surprise me) it looks like ICH has accomplished what shouldn't work with their 500.
They are working with:
a deck height of 9.40"
6.200x2.100 rods
4.150 crank
.927” free floating pins
1.120" CH pistons x 4.374" @~13:1
figure to use a 0.048 compression gasket
I just figured that if they could stuff all that in 9.40" I could shorten the rods to 6", use a thicker gasket, drop the compression ratio and fit it in the 9.208" deck height... I could even run the pistons up into the heads if I keep the cam lift low enough and run steel H-beam rods to minimize flex. Heck, I think I could even play with the pin bushings to get it all in there.
Am I nuts? :wink:
I'm only shooting for ~10:1 compression with peak torque at 2,400rpm. I don't really care what happens to the torque or hp after that 'cause if my tires (40X17GroundHawgs) are broke loose at 2,400 and I'm pushing 650ft/lbs there is still plenty of umpf to keep the lugs blowing mud out to 6,500rpm. I should have about 550-600ft/lbs off idle and with a doubler and NP435 I can put that in slow mo at 128:1.
With a Ross stroker piston (ros Mopar 400 flattop#9949 1.120CH and 0.990" pin) and shooting for 12.5:1 compression with 0.003 Deck Clearance and 0.048 Compression Gasket in a 401 with late model 58cc heads and 4.150 crank:
Deck face height of 9.208 minus 0.003 desired deck clearance = 9.205 desired height
9.205 (minus) 1.120ch = 8.085 (X)
4.150 (divided by) 2 = 2.075 (Y)
8.085 (minus) 2.075 = 6.010” required rod length
This piston fits in a 9.980" block with 4.15" stroke and 6.768" rods, with 0.017" deck clearance, dome cc -4, ring grooves are 1/16, 1/16, 3/16.
If you subtract the .768 off the mopar rod to equal the 6" rods I'd use, subtract it from the 9.980 mopar deck height that leaves 9.212" which is only 0.012" greater then the AMC deck height... so I think there is room to work in there somewhere.... with a custom piston.
Elliot;
The 9.4 inch deck height makes a very big difference, ICH gets 498.87 cubes but the numbers you quote are also .149 over my table values, 4.374 bore vs. a 4.225 bore giving them an extra 4.38875 inches per cylinder and they get an extra 3 cubes per piston with the additional .2 deck height - 7.38875 per cylinder for a grand total 59.11 additional cubes. The extra .2 inch of deck height on the block also brings the rod angle back to about 19 degrees. If you use a 9.4 deck height in my table you will run out of piston at a 4.135 inch stroke with a 9.3 to 1 compression ratio. Funny thing is 4.135 - 3.92 is .215. .215 is about the difference between 9.208 and 9.4. How about that :? The deck height on my 401 block is only 9.208 inches tall and that is what the table is built on. So bottom line is I still don't think you can get 500 cubes from a 9.208 inch block. I would hate to see you waste a lot of money on a project that will not work. Where did ICH get the 9.4 inch block?
Lets look closer at the 4.150 stroke in a 9.208 deck height block with a six inch rod instead of a 4.135 inch stroke with a 6.25 or 6.35 inch rod. stroke divided by 2 is 4.150 divided 2 is 2.075. Take the 2.075 and add a 6 inch rod and we get 8.075. Now take 9.208 and subtrack 8.075 and we get 1.133 inches. We have 1.133 inches to play with. Now, if we keep the oil control ring out of the piston pin we also must subtract one half the piston pin diameter. If we use a .927 inch pin we must subtract half of .927 from the 1.133 inches we have left. So 1.133 minus .4635 leaves us with .6695. Lets examine what this .6695 has to do. This .6695 must contain the ring pack and the dish (there also has to be about .005 clearance between the pin and underside of ring pack material). If we use a standard 1/16, 1/16, 3/16 ring pack with 1/6 between each we get a ring pack of 7/16 or .4375. Subtract .4375 from .6695 and we have .232 in left over. A 10 to 1 compression ratio will mandate a dish of about .24, maybe a few thousandths less. You are definately on the edge for I think your top ring is into the dish edge material, not a good thing. Considering the bore you plan you may get by with less dish. If you did manage to keep the ring pack in the solid portion of what is left of the piston, you might make it with a six inch rod but your rod angle will be 2.075 divided by 6 is .34583. Inv sin of .34583 is 20.2324 degress. I consider a 20.2324 degree rod angle to be excessive and chose to use a 6.25 and 6.35 inch rod in my table, you may not. I would not run this combo in a daily driver. This build would be pure race and is out of bounds for me. I think we are seeing the reason the big block Ch*vy is offered with 10.2 inch vs. 9.8 inch deck height when using a stroke greater than 4.35 inches. The ch*vy engineers are not willing to accept a rod angle greater than 19 degrees.
If I won the 401 currently up for raffle at only $8 per ticket (can you believe that?), I would stroke it to 3.92 with a 2.00 6.125 inch ch*vy rod and stick it in a Wagy. Actually, It sounds like a very sweet motor and needs no further help. It would power the wagy just fine as is.
You have been listening to me spout off about excessive rod angle. Try this on, keep in mind I’m not an engineer but the numbers speak volumes. I let excel draw some pictures for me today, pictures are worth a thousand words. I built three data pages (finally a use for that trig class), one with the stock 3.68 stroke, one with a 3.82 inch stroke and one with a 4.15 inch stroke. I then graphed the results. There’s definitely a significant difference between the 3.68 curve and the 4.15 curve. As much as I'd like to post the data table to this page, they are rather large (182 lines per set). Instead I’ll post a few key values.
For the stoke 3.68 inch stroke, 5.85 inch rod
Crankshaft
Deg After TDC….Piston Travel…..Rod Angle
………….....…………in Inches…………………..
0………………………0……………...... ..…0
10…………………...02795………….3.1309
20…………..…….…11097……….…6.1756
30……………….....24651………….9.0482
40…………………...43048…………11.6642
45…………………...53892…………12.8504
50…………………...65727…………13.9422
60…………………...92000…………15.8066
70…………………1.21068…………17.1912
80…………………1.52049…………18.0443
90…………………1.84000…………18.3324
You will notice in the first 45 degrees of crankshaft rotation after TDC the piston travels only .53892 inch or 14.64% of the total stroke. In the next 45 degrees after TDC (45 ‚Äì 90) the piston travels 1.30108 inch or 35.36% of stroke (for a total of 1.84 inch or 50% of stroke). If you plot the piston travel with respect to degrees of crankshaft rotation for the whole 180 degree power stroke you get a very nice ‚ÄúS‚Äù curve or ¬? of a bell curve. The points I provided in all three examples only plot to 90 degrees. The other 90 degrees is like a mirror image with point of inflection at 90 degrees (I think I said that right) The rod angle graph makes a nice parabola if you graph the whole 180 degree power stroke.
For the 3.82 inch stroke, 6 inch rod:
Crankshaft
Deg After TDC….Piston Travel…..Rod Angle
…………….....………in Inches…………………..
0………………………0……………...... …0
10…………………...03509………….3.4823
20…………..…….…11519……….…6.2505
30……………….....25589………….9.1585
40…………………...44685…………11.8073
45…………………...55943…………13.0085
50…………………..68227………….14.1143
60…………………..95500………….16.0028
70…………………1.25674…………17.4057
80…………………1.57833…………18.2701
90…………………1.91000…………18.5622
You will notice in the first 45 degrees of crankshaft rotation after TDC the piston travels only .559 inch or 14.63% of the total stroke. In the next 45 degrees after TDC (45 ‚Äì 90) the piston travels 1.351 inch or 35.36% of stroke (for a total of 1.91 inch or 50% of stroke). Percentages are virtually identical to 3.68 example. Again, if you plot the piston travel with respect to degrees of crankshaft rotation you get a very nice ‚ÄúS‚Äù curve or ¬? of a bell curve. The rod angle graph makes a nice parabola with only slightly steeper sides than the 3.68 graph.
For the 4.150 inch stroke, 6 inch rod
Crankshaft
Deg After TDC….Piston Travel…..Rod Angle
………………......……in Inches…………………..
0……………………....…0…………….. ......…0
10…………………...03152………….3.4429
20…………..…….…12514……….…6.7930
30………………......27800………….9.9574
40…………………...48546…………12.8440
45…………………...60775…………14.1547
50…………………...74121…………15.3624
60…………………1.03750………....17.4276
70…………………1.36531…………18.9642
80…………………1.71468…………19.9122
90…………………2.07500…………20.2327
You will notice in the first 45 degrees of crankshaft rotation after TDC the piston travels only .60775 inch or 14.64% of the total stroke. In the next 45 degrees after TDC (45 ‚Äì 90) the piston travels 1.46725 inch or 35.35% of stroke (for a total of 2.075 inch or 50% of stroke). Percentages are virtually identical to 3.68 and 3.82 example. Again, if you plot the piston travel with respect to degrees of crankshaft rotation you get a very nice ‚ÄúS‚Äù curve or ¬? of a bell curve. The rod angle graph makes a nice parabola with noticeably steeper sides than the 3.68 and 3.82 graph.
Lets look at the rod angle curves. The significant difference is in how steep (slope) the curves are. If we use the derivative (finally a use for the calc class) we get the slope of the curve. The steeper the slope the more inefficient the engine becomes because more and more of the downward force is directed away from the bore axis because of the increasing rod angle. Also note that the rod spends a great deal (from about 31 deg ATDC to about 149 deg ATDC in all three examples) of it‚Äôs power stroke at over ¬? of the maximum rod angle. This implies that for over ¬? of the power stroke energy is being absorbed by the block (all inclusive) in the form of side force (heat) instead of down force. The key is how much side force is too much. Lets pick the point, 31 degrees ATDC, where the rod angle first exceeds ¬? of it‚Äôs max value. Note that cos has a max value of 1 at 0 degrees and decreases to 0 at 90 degrees. Note also that our curve peaks at 90 where the slope would be 0. Derivative d(sin u)/dx = cos u, (I looked it up on Google) let u = 31 deg. Our curve formula is (¬? stroke * sin u)/rod length. The slope for the 3.68, 3.82 and 4.150 stroke curve at 31 degrees respectively is .2696, .2729 and .2964. Now we need an automotive engineer to step in and say if the mains, rod journals, piston pin and cylinders can withstand that amount of deflection indicated by the graphs and calculated slope. For a long life, daily driven vehicle (I say again, for a long life, daily driven vehicle) I say yes for the 3.82 using 6 inch connecting rod but I say no for the 4.150 with a 6 inch connecting rod. Use a longer rod, say 6.125 or 6.135, I‚Äôd say yes, but a longer rod will not fit with a 9.208 inch deck height, standard ring pack and 10 to 1 compression ratio. Need I say yes for the 3.68 example? Someone might want to do the force vector analysis next, might yield interesting results. Does Fuzz401 have any insight regarding design history of the AMC 401?
Elliott
07-31-2004, 10:05 AM
Regarding your ICH question, they cast the 500ci blocks from the design Herman Lewis put together.
Regarding rod angle, remember that ICH is running only ~0.55* less on a high rpm motor built for 600+ftlbs. What I don't know is that the ICH motor may actually have a significant amount of chatter at lower rpms that smooths out after 3,500 or more rpms, which would be above my peak of 2,400. From what I understand the 360 and 401 at ~18.30* made enough noise that the pistons on the low compression motors were offset .0625 inch toward the major thrust side. (out of curiosity how much would this effect the rod angle?) Why this wasn't done on the higher compression motors I don't know. Possibly the higher compression pistons had just enough more height to compensate for the side load and reduce vibration?
I realize that I am pushing the envelope to the extreme, but this isn't for a daily driver. The level of functionality is something I'm not sure could be computed based on formulas (although I will say the desktop dynos are very impressive) given that everything would fit inside the 9.208" block. There are probably more variables in the actual design and use of specific parts to be computed then formulas could completely diagnosis. Maybe I'm wrong about this because I don't know enough about using formulas to figure the specific dynamics, but computing the actual effects of rod angle in the 9.208 block would be effected by everything right down to atmospheric conditions, specific fuel grade and possibly valve timing... not to mention the specific weight of each component, specific rpm and the viscosity of the oil used.
Thanks for making sense of some of the math for me, I'm not too shabby in physics, but that's about the end of it for my mind. :mrgreen:
Elliott is right. The mathematics only go so far, in that the formulas estimate the boundaries and make the builder aware of just how far they can go and the associated pitfalls of being on the edge. From there the builder must take into account every known variable and decide how far to push. My build is intended to maintain as close to stock geometry as possible while gaining a few (at least a 100+ across the entire rpm range) ft lbs of torque. Elliott is pushing the envelope and his build, if he can keep it together, will definately establish a new level of AMC performance. I hope it works.
:? Update update update :?
Turning some wrenches. The Wiseco pistons on the Manley steel H-Beam rods with the 3.82 inch off-center ground crank and the Crane hydraulic roller cam work perfectly. Clearances between rod and block, piston skirt and crank, cam and rods all exceed .060 by a considerable margin. The pistons could have been .015 taller, need to shave about that much off the top of the block. Ordered from Bulltear the Edelbrock Pro Flo EFI and nickel plated front cover/oil pump. Rotating assembly is balanced, block is blue printed. Heads are next. This poked and stroked 401 (421) is going to generate an impressive amount of torque, very good HP and get fairly decent gas mileage.
jeepsr4ever
01-18-2005, 01:59 PM
Will you be dyno-ing this engine?
Dusty
01-18-2005, 04:04 PM
I hope you dyno it i regret that i didnt have the $$$ or the time to haul my setup back out and dyno it.
Good Luck.
Elliott
01-18-2005, 06:36 PM
That's sounding pretty sweet, thanks for the update.
On the 500CI I was looking at I talked to someone who'd been involved in similar builds and said it fits, works, is pretty impressive, but in their race applications the remaining block after the bore/sleeve was too weak and caved eventually. I was only planning to run around 9.5-10:1 compression and wouldn't likely exceed 6,500rpm.
I'm real interested to see how your's turns out :sa:
Elliott, good morning;
Are you still looking at the 9.4+ inch deck height? Because a 4.15 inch stroke in a 9.28 inch block is definitely too tight. After examining the clearances in my block I would not go over a 4 inch stroke, and then I would not use this as a daily driver. If you go with a stroke greater than 3.8 inch in a 9.28 inch block your rod angles will increase past an acceptable level, for me that is 19 degrees, and the engine will be stressed considerably between both sides of 60 degrees before top and 60 degrees before bottom. A greater amount of the fuel burn energy is lost to side load forces as the rotating assembly forces the rods to make radical directional changes while moving the piston a relatively short distance. Refer to previous post for piston travel vs. crank rotation data. I believe your reference to the 500 CI build above bears that out, plus the bore required leaves little on the 4.75 inch centers. I still maintain for your application you are better served with a taller block. If you can make 500 CI from an AMC block work, my hat is definitely off to you.
Elliott
01-19-2005, 07:55 PM
Stroking to 4.0 in the stock block may be the max.
Here's the advice I got on it:
"...I thought I would give you some answers to the 500" AMC cast block idea you have.
It has been done. The engine made some respectable numbers on the dyno but with time the sides of the block "let go" and the results were ugly.
When the block gets bored out to install the larger bore sleeves the material across the deck of the block between the cylinders gets weakened too much. Although the head bolting helps keep this area together it's just a matter of time before it will let go.
Fred Brewer of AMC race fame has built such a engine and feels the block is too weak for the big bore size. He has however bored out using the AMC cast cylinders to 4.31" no problem. The blocks are filled to the top with block fill and the heads are reverse cooled via a remote water pump.
With a 4" crankshaft this makes a 468" AMC engine. Fred (and others) have twisted out over 1000hp from these engines using his race AMC heads/intake manifold.
The bore centers are the same as the Mopar 440, it's really the short deck height that I consider to be the ultimate obstacle. I'm not so sure the cylinder wall thickness would be the same concern if I wasn't shooting for 500hp and turning 9,000+rpm. Not being able to use the extra head bolt is a concern however. I haven't ruled it out entirely. We're only talking +.150 here... (I can very head gaskets and pushrod length to pick up ~half that) I'm only looking to build low end torque on pump gas and iron heads not high end HP on blown fuel. I don't think the demands on my engine would compare at all.
Out of curiosity, didn't AMC compensate for some of the steep 401 rod angle by using pistons with pins offset to the thrust side?
Here are a few money issues I’d like to share others considering a similar build. First the Edelbrock timing chain set will not work with a roller cam. The roller cam requires a keeper plate bolted to front of block to control cam end play. My machinist chose one from a Ford block (all aftermarket kits are basically the same thing). The plate is about .135 inch thick so you have to remove the corresponding thickness of this plate from the timing set cam gear. There is not enough material in center of the Edelbrock set and holes appear in center portion, weakening the gear considerably. I ordered a billet steel set with a provision for a torrington bearing (a torrington bearing is a flat bearing that sets between cam gear and face of block designed to prevent the gear from riding on block face and is about as thick as the Ford cam keeper plate) from Mad Dog Racing, cost about $30 more than the Edelbrock set. The off-center grind required the balancer to chuck crank in lathe and turn material from the counter weights rather than bore holes, this cost an additional $25 (turned out very nice). I still think this build produces the most additional cubes for the dollars spent.
Check out the March 2005 edition of Car Craft Magazine. They have an article describing a 500 (498 actually) ft/lb 401 build. The article briefly mentions an off-center crank grind option utilizing 6 inch sbc rods for even more torque. Article also makes mention of a .030 limit on cylinder bore of AMC block (not sure about that one). They list some very impressive torque/hp values generated from standard 3.68 stroke employing a fairly aggressive cam and standard carb. My motor with less aggressive cam, stroked to 3.82 utilizing the Edelbrcok Pro Flo EFI might come very close to duplicating those numbers. Check it out.
Dusty
04-11-2005, 09:40 AM
On a side note wasnt there a stroking method where you used mopar 340 rods with overbore chevy flattop pistons and it left you .040 down in the cylinder?
Update. Took a little detour. In the process of removing 4 to 5 cubic cms from the combustion chamber to compensate for longer stroke and change in piston design from stoke (compression ratio comes in at 9.2:1), I decided to install larger valves. Just got them back from machine shop - valves are enormous. Will post specific size when I get a chance to talk to machinist. Getting closer to having this beast together and running. Also, there is a post by Radamx (?) in the engine section, page three, titled dino results are in. His 401, stroked to 3.825, bored to 4.25 made over 1100 hp and 1000 ft pounds of torque below 5800 rpm (dual stage nitrous). That is very, very impressive! Note the bore and stroke selected, further evidence the 3.8 stroke is the way to go. Also, I ordered the matched cam distributor gear set from Bulltear, one word – phenomenal. Everything I’ve ordered, fuel injection, nickel cover, fill tube, and gears have arrived on time, as advertised. Thanks Bulltear.
A couple of new things. The AMC V8 ARP head stud kit is not compatible with a 3/8 inch header flange because the stud is too long, and the six-point nut and washer assembly sits too high. The rest of the studs could be at least a 1/2 inch shorter also. I order six 3 3/8 inch studs and 12 point nuts and will mill .26 inch recesses in the four corners to allow the nut and washer assembly to stack to less than .350 inch as to equal the original head bolt head thickness. I have tremendous respect for ARP but I do wish they would do a little better job assembling kits. I selected the Doug Thorley Tri-Y header for it's low end torque building characteristics. Also I purchased the Advance Adapters AMC V8, NV 4500 29 spline output, Dana 300 full bell housing kit. Did you know you have to shorten the NV 4500 output shaft .25 inch before you can bolt to Dana 300? Says so in directions. Another oh $hi! during assembly.
jeepsr4ever
09-13-2005, 10:49 AM
You sure are doing some fine work. You should be taking pictures along the way sir.
Dusty
09-13-2005, 11:38 AM
A couple of new things. The AMC V8 ARP head stud kit is not compatible with a 3/8 inch header flange because the stud is too long, and the six-point nut and washer assembly sits too high. The rest of the studs could be at least a 1/2 inch shorter also. I order six 3 3/8 inch studs and 12 point nuts and will mill .26 inch recesses in the four corners to allow the nut and washer assembly to stack to less than .350 inch as to equal the original head bolt head thickness. I have tremendous respect for ARP but I do wish they would do a little better job assembling kits. I selected the Doug Thorley Tri-Y header for it's low end torque building characteristics. Also I purchased the Advance Adapters AMC V8, NV 4500 29 spline output, Dana 300 full bell housing kit. Did you know you have to shorten the NV 4500 output shaft .25 inch before you can bolt to Dana 300? Says so in directions. Another oh $hi! during assembly.
A clocking ring will alleaviate the problem of the output being too long. i went with the longer female input on the t-case and then a clocking ring without shortening the output on the tranny and it worked great. the stock input had the same problem you are describing. i too have the AA full bellhousing...... if you add the clocking ring since it is 3/4" max thick you will only loose roughly 1/2" of engagement not enough to even worry about stripping the splines off.
my old cummins conversion took alot of abuse and had a collar between the tranny output and tcase input that didnt have much for spline engagement 400k miles later and 800-900ft/lbs of torque and a 30k lbs gooseneck behind that most of its life the setup hadnt twisted off the splines...........
MrFurious
10-25-2005, 12:54 AM
Updates? Pictures? Come on man...it's been a month, you're killing me! :!:
Actually, reading through this thread has been helping me a lot in regards to stroking my 360 to a 406. Now I'm no mathematical whiz like J20 here, so I'm hoping someone can help me out with this a few things.
1) Assuming a 4.11" bore in the 360 (+0.030"), 3.827" stroke, 6" SBC rod length, and a compression height of 1.29" on the piston I'm getting a scant 0.0045" deck clearance. Dropping back to a 1.275" compression height, I'm still only getting 0.0195" deck clearance.
9.208 - 1.9135 - 6.0 - 1.29 = 0.0045"
9.208 - 1.9135 - 6.0 - 1.275 = 0.0195"
Even adding 0.050" for head gasket thickness only bumps them up to 0.0545" and 0.0695" respectively.
That sure doesn't seem like much deck clearance, and more importantly what will piston-to-valve clearance be like? Shave the deck a little to square things up and you'd really be skinny on clearance.
2) The 360 rod journal width is 1.998 to 2.004", while the 401's is 1.846 to 1.852". Would I have to comensate for this difference in some way, or won't it make a difference? I figure it wouldn't be hard to widen the 401's journals while grinding them down, but is it necessary and will it cause excessive side clearance with the SBC rods? My main concern here is ensuring the rods are centered up in the bores and not in a bind at the crank leading to premature rod bearing failure.
3) Oddly enough, when I plugged this all into a compression ratio calculator using the 33cc dish, 58cc combustion chamber and 0.050" thick head gasket, I cam up with a CR of 9.02:1.
From my understanding, you are removing additional material from the combustion chambers to gain 5cc's of volume for a total of 63cc. According to my calculations, this will net a CR of 8.65:1. Conversely, milling the heads to reduce the combustion chambers by 5cc to yield 53cc's, which by my calculations would result in a 9.43:1 CR.
Am I missing something here? If my calculations are correct (which they may not be), wouldn't it have been much easier to just reduce the piston dish by 5cc rather than working over the heads?
MrFurious;
Glad your getting something out of this thread. I went back to page three and edited the para on compression ratio, added a 9cc value for head gasket and nothing shaved from head, stock (58cc) combustion chamber, 33cc piston dish will yeild a 9.3:1 compreesion ratio with a 3.82 stroke and 4.195 bore. I did not shave a significant amount off the heads and did open the chamber to install bigger valves. My 33cc dish finished at 9.1:1. Here is why - I finished with a 863cc bore and a 61cc combustion area and 9cc gasket. 863 + 61 + 9 = 933. Now divide 936 by 103 ( chamber, 61 + gasket, 9 + dish, 33) and you get 936/103 = 9.058. I finished a shade under 9:1. I devalued my compression ratio to improve towing (debate?) and decrease my dependency on premium gas. Here is another factor to consider and crucial to the 33cc piston dish - eventually I may want to run a little boost - I can perform a fairly simple head swap, and go supercharged. Probably won't have to but at least the option is there without having to change the pistons. The cam selected and multi port EFI (may not need a new chip or fuel adjust depending on boost level. 5 to 6 lbs may require no modification at all) will support this. Hence the Manley steel rods, forged pistons, balanced.....
Blown7
10-27-2005, 07:08 PM
Not to seem too smarty pants but you are going to have to install a big CC chamber which I don't think it can be made from a AMC head if you want to add some boost. At 6 lbs of boost at 9-1 compression your around 13.4 final compression which for me is way to close to detonation with no igniton retard for even good pump gas on a a zero degree day. I have 64.4 CC chambers with 2.090 and 1.750 valves unshrouded right to the head gasket ring with a 7.75-1 compression ratio. JE pistons had all they could do to keep the top ring land sturdy with a big dish to get down that low and still have room for a .990 inch piston pin. I am very interested to find out what kind of head, and the machining it would take. What are your plans on installing a head easily to get a compression ratio down below 8-1 for even mild boost? I know going open chamber will yeild about 11 CC's or so. Thanks, Jeff
Good point, 6 pounds is too much for this application. Not sure how to handle this one yet.
tarior
10-28-2005, 03:45 PM
I'm sure I've been on this tack before, but I must say that if all the poking and stroking weakens the block and sets the rod angle too severe, then why not go small displacement with LOTS of boost? I'm not in a position to build a high dollar race motor, but I'm sure someone out there is. Just look at what people have been doing with small block Fords. :-|
Find an amc 327, early model, will handle a lot of boost.
Blown7
10-29-2005, 01:51 AM
I'm sure I've been on this tack before, but I must say that if all the poking and stroking weakens the block and sets the rod angle too severe, then why not go small displacement with LOTS of boost? I'm not in a position to build a high dollar race motor, but I'm sure someone out there is. Just look at what people have been doing with small block Fords. :-|
You can, but conversely now if you want a daily driver, and a weekend warrior a big boost engine will be not fun to drive on the street, act just like a radical normally aspirated engine (lousy idle, race gas, hp and torque band in the high RPM's, roller lifters that need constant adjusting, high maintenance). Every engine has a mission specific profile, I think that everyone just wants a great performing engine without all the hassle of babysitting it. Thats why a mild restroke and bore or better yet (and more expensive) a mild huffer gets the most bang for the buck. Remember NOTHING beats cubic inches either normally aspirated or blown thats why big cubic inches is a great place to start. Thats why my next build is the Indy 500 cube blown. That engine has alot of potential for big HP and Blown and still be a daily driver. I'm thinking 750 to 900 hp @ 3500 RPM and maybe 200-300 HP at idle. Torque off the scale at both ends, lots of parts downstream to modify to hold up to that engine. Jeff
tarior
10-29-2005, 03:12 AM
Find an amc 327, early model, will handle a lot of boost.
I was thinking Gen II or III AMC, the small block Ford isn't as strong as any AMC, yet those guys are running 8's in "street driven" Mustangs with centrifugal blowers.
Gremlin4ever
12-26-2005, 10:18 AM
Wow! I made it to the end (so far anyways) of this thread. I for one am big on large displacement engines :lo1l:
Didn't see any pics, but don't let that mess with your focus on details in your building process. But after you assemble, disassemble a few times to check all the clearances, a few pics would do us wonders as your final assembly takes place. Take your time with this assembly as we wouldn't want to see you miss a very important task somewhere in the build.
Attention to detail is more important than us looking at pictures :t:
jeepsr4ever
12-26-2005, 10:38 AM
401 = 50.125 cubic inches per cylinder
401 Bore x Stroke, 4.165" x 3.68"
2.54cc in one inch
2.54 X 2.54 X 2.54
16.387 cc's in a cubic inch
3.539 cubi inches in a 58 cc head
3.552 ci left over in the combustion chamber for 8.5-1 compression
Change in volume 8.5 / 9 = 5.6% of the 58cc dome in the head
.1981 CI needs be milled away or 3.246cc's to gain .5 bump in compression
hmm a liquid test will tell you how much you will need to take off...58cc's of liquid will fill the combustion chamber on the head and to gain .5 boost in compression over 8.5-1 you will need to remove 3.246cc's which at this point tonight I cant tell you how much that would be off the head. May be around .022"
Gremlin4ever
12-31-2005, 08:21 PM
Muscle Car Review, annual 2005 and is to be displayed until March 14, 2006
Get this issue fast! It has an AMC 401 build up with 498 lbs-ft of torque! Though it is at 4600 rpms it is a very interesting read.
Briteblock
01-17-2006, 08:35 PM
You guys stroking to 3.850? Carrilo makes a nice rod that takes a small honda bearing like MC was talking about. I am at his shop and am a welder here...he has a 401 on a stand and I think its a stroker. MAybe with enough probing we could get him to give up all the info :scratch:
thigh19
02-13-2006, 09:38 PM
What about an offset grind to the Crank?
I'm back and work continues on the bored/stroked 401. I'm building the run stand now. I want to run it in the garage first. I installed the Milodon external feed oil pan (one line), a dual remote oil filter, a Powermaster 140 amp alternator, a BeCool aluminum radiator with dual electric fans, a Flow Kooler water pump, a AGR power steering pumb and Super Box 2. The Edelbrock Pro Flow Multi Point EFI looks awesome, as do the classic finned aluminum Edelbrock valve covers, I do need to order the control chip from Edelbrock. I also finished the Dana 300 with a 4:1 gear set, 29 spline input and 32 spline outputs, do need a dual stick shifter. The NV 4500 is also ready to go with Advance Adapter AMC V8 complete bell housing kit. This combo just might move the J20 smartly down/off road.
jeepsr4ever
10-18-2006, 10:15 PM
Loca l builder here has had GREAT luck getting 700hp on pump gas offset grinding a 401 crank and using these Eagle rods
CRS6000HJ 6.000" lightweight, 1.890" "Honda" journal, 570g $625.33
Thats 700hp with a small camshaft and not much tweaking, but thats stroking her .358" :t: :t: :t:
Granted the crank will need to be ground ($600 MAX)
The rods will have to be bought ($625)
Custom pistons with lower ring lands ($800)
And this scenario will yeild 446CI at .030 IIRC
Now lets talk filling the block, over boring and sleeving + O-ring'n, 464CI at 4.28 bore.
ericruhl
11-14-2006, 05:59 PM
The pistons could have been .015 taller, need to shave about that much off the top of the block.
About half of that .015 is a math error from this post (http://www.bulltear.com/forums/viewtopic.php?t=1473&postdays=0&postorder=asc&start=67).
3.82+ 6.00 + 1.275 = 11.095, not 11.102. So 11.118-11.095 = .023 deck clearance, .007" more than your expected .016. Any idea where the remaining .008" came from? Was the piston compression height off from your expected 1.275"? Sorry if I missed the answer in the thread, I didn't see it. And why did you shave the block, was it to recover the desired compression ratio?
I'm exploring options to follow in your footsteps ;) which is how I found this thread. I'm interested in offset-grinding the crank to increase stroke in combination with the 6" SBC rods to keep rod angle within reason, however I'm looking for a little more compression (~10-10.5). I'll call Wiseco to discuss a custom piston, but wanted to fully understand your build first. Currently I've come up with these numbers to get my desired CR:
Stroke = 3.820 (place holder for now, a spun bearing will limit my stroke options)
Bore = 4.190 (same as your pistons)
Head volume = 57.92cc (stock)
Head gasket volume = 11.34cc (stock)
Piston volume = 20cc
Compression height = 1.290 (1.275 + .015 from your build)
If my numbers are right, that yields 421 cu. in. with .008" deck clearance and ~10.5:1 CR. ??
Excellent writeup btw, thanks for sharing! :)
I'm glad you spotted the error before start. This discrepancy was corrected by Wiseco when the pistons arrived. Did not have to shave block. I had 3.5 cc taken out of each combustion chamber to bring the compression ratio down to 9.3 to 1 and allow for larger than stock valves. I can't always get 91 octane gas. The piston dish could be made smaller and get a 10 10.5 to 1 compression ratio. I get some time off during the holiday and hope to start this engine on the run stand.
ericruhl
12-06-2006, 08:06 PM
I had 3.5 cc taken out of each combustion chamber to bring the compression ratio down to 9.3 to 1 and allow for larger than stock valves.
Previously you mentioned "the new plan is to use a bigger intake and exhaust valve, .208 and .176". I'm guessing you meant 2.08 and 1.76, is that what you ended up with? The AMX valves were pretty close to that at 2.08 and 1.74 (assuming I read that correctly).
I get some time off during the holiday and hope to start this engine on the run stand. Woohoo! Good luck! :)
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