Thumper 401?

[shimniok]

I have a pretty good challenge that I think most people seem to have no answer for... Maybe you can help? This is long.

I have an FSJ (86 GW). It weighs 5500#. It has a 3 speed auto with low stall converter. It has tall gears (33" tires, 3.73:1) and a 4" lift. I take it four wheeling. It has a 3" exhaust with Magnaflow muffler.

The 360 in it now was rebuilt about 10k miles ago. It has a Comp Cams 260H, AFB, Edelbrock dual-plane Performer, and 8.5:1. It STRUGGLES to get me up the rocky mountain passes west of Denver. The only way to get up most passes without my foot to the floor is to run 2nd at 55-60. I want more power. Do NOT tell me I haven't tuned it right after 2 years of trail and error-- and improvements-- unless you plan to drop by this Saturday and fix it for me. :D

I run 2000-2800 rpm in the 40-75 mph range. About 2600 @ 65. I have virtually no power in this rpm range as evidenced by lots of throttle to get up even slight hills and slowdown on big hills at altitude. The auto trans never lets the motor see more than 4000rpm by the way so the Chevy answer of building all the power from 3500-5500rpm isn't going to work. :D

I now have a 401 in the garage waiting to be built. Your challenge is-- can you build a motor that will solve my power woes -- without changing anything else about the vehicle? You are allowed to change exhaust. :) How would you build it?

What I really want to know is what kind of torque curve would you shoot for??? What power band would you select? Would you rather have more hp at 4000 or more torque at 2000? Or a balance?

Does any of this make sense? Am I insane? Wrong? Stupid? :D

Many thanks!!

Michael

[jeepsr4ever]

Welcome aboard Mike!!


First I would use a aluminum intake or possibly MPEFI (if in the budget) just cam/pistons/intake/carb alone would do the trick on a 401. I woudl warm it up a little with 9.6-1 speed pro's. Its a real basic build to get ample power for your rig out of a 401. Fuzz or tufcj will probly come around and go into more detial. Let meknow if I can help in any way


-MC

[tufcj]

Mountains suck.... The best way I've found to get up to the tunnel is "turbo diesel". My EFI 360 CJ struggles up too. I'm running 37" tires and 4.27 gears. I'm going to 4.88s as soon as I can get the jeep in the garage.

You really need more gear with 33" tires and that kind of weight. I'd say at least 4.11s, and maybe 4.56s. (I'll give you a great deal on my 4.27s if both of your axles are Dana 44s). The only way to keep up speed in the mountains is to have the engine spinning near the top of it's power band. You also have a problem with a carbed vehicle. Even if it's jetted properly for the 5000 ft. elevation of Denver, you need to go DOWN a jet size for every 2000 ft of elevation gain. At the tunnel, 11,000+ elevation, you're rich by at least 3 jet sizes, your engine just can't get enough oxygen to burn the fuel it's being fed. Without enough air, the timing needs to bump up too. Things you can't control automatically without a computer.

Where are you from. I'm in Aurora, CO.

Bob
tufcj

[shimniok]

Thanks for the responses so far! The advice is VERY valuable.

The reason I didn't want to change anything but motor is I just spent $1800 on rebuilt, locked and regeared axles. Now I'm married and spending $ is... limited. :)

I wanted to keep hwy rpms to stock level. A mistake? Maybe. But get this...

A friend has an 87 GW, 33" tires, 4" lift, roof rack, very similar to me, but runs 3.31 gears and a 401 with 10:1 CR and mild/stock cam plus a Quadrajet which he just got dialed in a few weeks ago. He is now running 3/4 throttle in 3rd up that first big hill on 285 to keep up with traffic running 60-65. He runs most passes in 3rd. I've personally seen this truck PULL AWAY RAPIDLY from me on hills where I am foot to the floor to hold 55-60 in 3rd with only modest accel in 2nd. On Monarch Pass I was in 2nd where I could accelerate ok but he STILL pulled away quickly (I think he was in 2nd too). I've also seen him accelerate from 65 to 100 on nearly flat ground where I could barely make it to 80 in the same timeframe. Frankly it is jaw-dropping to see.

So, that is what is possible. Btw, Spitfire built his motor.

I've been playing with Desktop Dyno a lot (just ordered the 2000 vers). I modeled my motor and his as best I could. What I've found is my Comp Cams 260H is a horrible choice with stock CR and exhaust, weak on torque in just the rpm band I most use. He has like 100 lbs-ft on me with his combo.

In a 401 with 9.5:1 CR, small tube headers, the Edelbrock Performer cam puts out 430+ lbs-ft in 2000-3500 range, and with 320 hp @ 4000 (best of 260-ish cams). Factory Pontiac grind specs I found on the web puts out 440+ lbs-ft from 2000-3000 (447 @ 2500, 'only' 435 @ 3500 and 408 @ 4000) with slightly less hp @ 4000 (311 vs. 320). No other cam comes close to these two in torque. The next best are down 10-20 lbs-ft 2000-3000.

Seems the Pontiac grind puts peak torque @ my cruise rpm, most torque in the power band, and peaks hp @ 4000 suggesting good off-idle torque. I doubt 9 hp matters since it'll be 30 more than I have now. I think it's the best choice I've got. That's what I am leaning towards.

But this is all cloud pushing based on a lot of assumptions, book learning, and junk. What are your thoughts?

Also, EFI is planned too.

Michael

[cobra5laddict]

your cherokee is not a red white and blue 2 door with 33's is it? i see that truck here local running around. i am in arvada and went to school in gunnison... i know that 285 drive all to well not to mention monarch. i had a 79 cj5 with a new stock 304 and a 3spd t-150 with 31's the gears were 3.54. throughout most of the large hills and monarch i had my foot burried into the floor board. i could never muster 50 mph in 3rd. 2nd sounded like i was winding it too tight. although i had a 2 bbl.. on the 360 i am building (different jeep) i am going to run tbi.. i bet that will make a bit of difference.

[fuzz401]

might want to go to 9:1 or 9.5:1 cr and might want to look at the comp 268 cam

[shimniok]

Mine's a white GW with woodgrain, 33's, roof rack. I live in Centennial.

http://www.cfsja.org/rigs/michaels/tc/index.html

Thanks for additional replies!

What D.D. sez is higher CR (9 or 9.5) and small tube headers is the only way to make good power at low r's with stockish cam.

Pontiac specs looks best to me so far; ideal match to my rpm...

I am going to call a couple cam shops and engine builders for advice too.

Desktop Dyno 2000 is on the way to help too.

Michael

[jeepsr4ever]

That really looks like a jeep I saw in FSJ magazine

[cobra5laddict]

SHIMINOK,


what are you going to do with the 360 in your rig if you go to 401? i might be interested if you would like to sell.


Byron@waringoffice.com :lo1l:

[Goose]

I am originally from Central City Co (moved here 5 years ago) and I have 5800# J-10 with a 360 I ran around up there all the time, While I wont say I had "ample" power at the tunnel I could easily have run 80 or better climbing either side.. I would suspect there is something out of whack in your set up, unless that cam is really hurting you. My 360 was essientially stock with a Edelbrock torker and 1406 carb with a mallory hyfire ignition box and headers. Bob is right in that at the tunnel it's gonna be a dog to a certain extent but it should still run pretty fair unless it's tired. So I guess this is a long way to say.. If I were doing it I would build the bottom end essentially stock, Maybe bump the C/R If you can swing the dough. But the money I would spend would be on the cam/headers and Fuel injection, With the best ignition system you can afford. I have always believed the ignition system is one of the best places to improve performance, since most other mods are aimed at getting more fuel/air into the engine..It seems the greatest gains would be made by making sure you can burn all you do get in there.

(Jeez I'm getting to be a wordy bugger)

[shimniok]

On the 360, planning to get a cheap FSJ without motor and swap in and sell the whole shebang to try and recoup cost.

I think the cam is hurting me. I am usu foot planted to hold 50-55 up to the tunnel. Motor is new. I've played with mix/timing for some time and improved power, but not lots. Ignition is already about as hot as it gets.

May install O2 sensor and tune carb more. Headers too. And may even try another cam. Hate to build a 401 without knowing what went wrong with the 360.

Higher CR is a must have as far as I can discern.

On the 80mph J-truck, what gearing, tire size, and cam? Thx.

Michael

[shimniok]

PS: Rig's barely visible on p15, Feb 03. Don't think there are other pics of it in its present state? My old 85 made cover in 01. Hoping to make Spring with an article about the St. Elmo area so rig may show up there. We'll see... :mrgreen:

Michael

[Goose]

Well on the J-10 the tire size was 33's the gears are 3:73 (I'm pretty sure)
and the cam was the edelbrock performer cam.. There is kind of a mismatch on the cam and intake as the intake is a torker (2500-7000) and the cam is off idle to 5500 if I remember right. but I think I would look into your setup something has to be out of line to be as doggy that.
I would really wonder about the cam. It seems if youre making power above say 2500 this is about where youre holding the grade, Kicked down climbing like that if it's holding 50-55 and if it shifts it doesn't have the torque to mantain it without kicking down and bringing the RPM back up into the power band,
Mine (since it is a 4 speed) would continue to pull in 4th if you let it until it got ahead of the cooling system at low rpm and start to get hot, then down into third and cooled right down. that stretch from georgetown to silverplume is the toughest pull on the hill.
If I remember right I was turning about 2700 at 70 mph
The one caution I have to add in here is Fuel mileage from Denver to silverthorne was about 4 mpg. 16-17 under normal conditions

[shimniok]

Thx. Sounds like our gearing is identical. I get 8-10 mpg depending on number of hills, hwy vs city etc.

Here's graphs of D.D. tq/hp for Edel Perf, CC260H and Pontiac 9779066.

http://homepage.mac.com/michael_shimniok/360Atq.jpg

http://homepage.mac.com/michael_shimniok/360Ahp.jpg

But sure, maybe it isn't tuned right, still. Would a degree of timing or being 1 stage lean or rich completely throw performance out the window?

...what is a sure fire way to set timing perfectly?
...what is a sure fire approach for dialing in carb?
...anything else I can do?
...how do I verify my 7 year hi flow old cat.conv. is not plugged?
...what else could rob lots of power?

Apologies if this is OT.

Michael

[Goose]

Well as for dialing in the timing, I use the "ping method"..Unscientific and If you don't pay attention and let it detonate a long time your going to break something but it goes like this. Set your timing about 5 -7 degrees advance from stock for altitude then go try it.. Keep advancing it till you start to ping at mid Low rpm full throttle acceleration. then back it off a little. as for the carb I dont have a good way, I usually judge by performance and driveability, you would have to be fairly rich to dump performance to the level you are seeing. If you were a little lean it would run better the higher you go. But you might save yourself some grief and pull that cat and put a "Test pipe" in it and see . even a partially plugged converter will degrade performance a lot. or you could find a station that has a old tail pipe sniffer exhaust analyzer (like they used to use for em tests before envirotest.)
Don't lose hope if that 360 is fresh it should drag that wag around in style.
What Carb are you running?

[shimniok]

thanx for the tips.

Running an old AFB. REALLY sick of the choke on it, can't get it dialed in. It does pull off fully, just too quickly (no heat riser). Maybe time for the EFI after all... (GM TBI) ... or a Qjet...

Will check out the exhaust issue, who knows...

Michael

[shimniok]

In case anyone's curious, I swapped on a Qjet, did some quick calibration, passed emissions, and improved performance (below 50mph). It drives like it has EFI at least below 50 and gas mileage went up quite a bit. It still is lacking on the highway. I haven't checked for the plugged cat yet.

Michael

[MrFurious]

Don't put a whole lot of faith in the DeskTop Dyno software, as it isn't very accurate in terms of real world numbers. When I worked down at Jeg's in the Tech Support Center, we actually plugged several crate engines into the software and none of them were even close on the HP and torque figures we got off the engine dyno. Typically, DD would show 50-75 more horsepower than was actually pulled off the dyno.

However, the power curves were usually pretty close in regards to peek power at such and such rpm, so using it to build an engine up for power in a specific range is possible. Just don't rely on the power numbers it gives you unless you want to be disappointed.

[shimniok]

Thanks for the info, that is good to know.

I noticed DD2k is significantly more optimistic than the original DOS-based version was (which claimed 95% accuracy and was closer to the original creator's vision I suspect).

I will keep that in mind and use it (and talk to some engine builders) to figure out what the best -curve- is for the setup I'm running. That's really the biggest question I've had all along, anyway.

Michael

[shimniok]

Thought I'd post again. I haven't done squat with the 401 yet. I am probably a jet size or two rich on the Qjet. I do have an EFI setup in the garage but that is a lot of wires to add and I'd hate to break down on the trail. That's why I never put it in. One of the guys on the CFSJA list runs an MPFI Edelbrock on his 360 and reports 90+ at the tunnel, but he also runs real low gears and stock tires and lift (so he must be spinning 4000 at hwy speeds?)

All the desktop dyno stuff I've played with says I can get 20hp and 70+ ft-lbs across the ENTIRE 2000-4000 range with a 401 and either an edelbrock performer or a custom grind like the Pontiac *066 (the latter is for big heavy Pontiacs with autos, the former is for small motors so puts the power lower in the bigger motor I guess). I haven't looked at all the possible cam grinds or called anyone yet. Have done a few searches here for cam advice.

I finally put together some money for the 401 so we'll see what work needs done to it and go from there. I'm also contemplating simply putting in a new bumpstick in the 360 along with headers. I hate seeing a $2800 motor go to waste or blowing a lot of money on the 401; I'm banking on it not needing any major machine work. Aside from lack of power the 360 runs fine.

If I do the 401 I am taking the advice here to heart: 9.0:1 or 9.5:1 CR pistons (or do I need to deck the block to improve squench?) headers if I can possibly afford it, and will keep the Edelbrock intake and Qjet carb, then do some kind of cam grind with 114* LCA and duration to support peak torque around 2800-3000, peak hp around 4000-4200.

Also to doublecheck I plan to take it to a muffler shop to see if the catalytic converter is bad after 8 yrs. (How else would I diagnose this?)

Michael

[tarior]

Also to doublecheck I plan to take it to a muffler shop to see if the catalytic converter is bad after 8 yrs. (How else would I diagnose this?)

Michael[/quote]

Take it off and look inside :mrgreen:

[shimniok]

Okey doke... I think I can probably handle that! :mrgreen:

[tarior]

The cat on my Nissan truck was plugged, I fixed it right up with a sleever bar :!: It flows great, now! Of course, there is no emissions testing where I live.

[shimniok]

Actually I guess I can't take it off... it's welded in... I s'pose I'll just take it to an exhaust shop for a look...

[Dallas Lemon]

I have recently finished the buildup of a 401 and installed it into my CJ7. The machine work was done by Heads By Paul in Englewood, and they did the normal 30 over and 10 under, balance, and supplied a 260H cam. Eutectic pistons were used with the stock CR. I decided to go with the Edelbrock heads instead of having the stock heads worked over, and using the Edekbrock heads increases the CR to 9.5 to 1 with the stock bore. All I can say is HOLY SMOKES! My CJ weighs in at around 4500 lbs. It has 4:56 gears and 37" MTRs. This engine has an incredible amount of torque. I was running a 360 that was stock except with a Performer intake and a 260H cam. This 401 may have as much as twice the HP the 360 had. And easily twice the torque. I contribute most of the power gains to the heads. If your 360 is in good condition, I would suggest installing as set of Edelbrock heads on it. You can use them on the 401 if you decide to swap down the road. You will not regret it!

[jeepsr4ever]

:t: Eddy heads do rock!

[shimniok]

I still have a hard time believing the 260H is the pinnacle of cams based on the Desktop Dyno output. I wonder what I'm missing...?

The Edel. heads sound great... probably way more $$ than I can afford, but c'est la vie. :mrgreen:

Michael

[tarior]

I've had good results with the 268H. I REALLY like the Crane 272/282. Streetable, VERY strong midrange.

[Dallas Lemon]

I still have a hard time believing the 260H is the pinnacle of cams based on the Desktop Dyno output. I wonder what I'm missing...?

The Edel. heads sound great... probably way more $$ than I can afford, but c'est la vie. :mrgreen:

Michael

My goal for this 401 was to have a a strong bottom end with decent power at mid range. The bottom end is much stronger than I expected, and the mid range is very strong! I can see now that I could have gone with a more radical cam and still would have good bottom end. As far as the 260H being the "pinnacle of cams", it depends on what you are going for. I was very pleased with that cam in my 360 and therefore decided to use one in my 401. I am not a high RPM high HP kind of guy. My CJ is built for the rocks, and the way it performs is exactly what I was building it for. My best guesstimate is it is easily making 350 HP, and maybe 400. The torque numbers have got to be 450, and it is making it at 3000 RPM or less.

[shimniok]

Hm... what altitude are you at? I'll post when I find the root cause behind my poor power. I have a 360 with 260H. Maybe it is something other than the cam.

Desktop Dyno (see graph earlier in thread) shows the 260H is mediocre 2000-3000. Maybe that is because all the power is below 2000rpm?

Michael

[Dallas Lemon]

Hm... what altitude are you at? I'll post when I find the root cause behind my poor power. I have a 360 with 260H. Maybe it is something other than the cam.

Desktop Dyno (see graph earlier in thread) shows the 260H is mediocre 2000-3000. Maybe that is because all the power is below 2000rpm?

Michael

Englewood is around 5300 feet. Have you had your cat checked yet? My CJ is registered in Estes Park and does not run a cat anymore. Just a 3 inch single using the stock manifolds. Like I said, the bottom end is SO strong in this thing. I can go around a corner and not need to downshift. With the T-18, it easily pulls out of corners at 800 rpm in 4th gear and effortlessly accelerates with the 37" MTRs. The 360 would struggle. I had a buddy several years ago that ran 401s in his CJ, and ended up with a 272 cam. We even ran it at Bandimere where it ran the 1/4 in the high 15s at 80 MPH with a T-18, 4:10s and 33s. It would see well over 6000 RPM, and he pushed it to 7000 on a snow run when his rev limiter was bumped up to 7200 unknowingly. It grenaded shortly after that. He went through three 401s and grenaded each one before going back to a 258. My personal feeling was they were too radical and didn't like the extended high RPMs he was pushing them too. I'm sure there are 401's that last at 6000, but not without modifying the oiling system. I'm getting side tracked. Bottom line is I wanted a strong bottom end engine and got one.

[Henry Lavrenz]

Turbocharger.

[MoPedal]

Reading this post really has me wanting a 401. Dallas like you, all I do is rock craw. :t: I run a 304 now (with a final drive of 99.9/1) in my scrambler and it runs fine but I guess I want MORE!!!! I like RPM's too! Your scaring a little on the 7000 #-o .
Is there a post that talks about taking a stock 401, doing some modifications (cam incl) to get the best low/midrange power possible? Is it powerful enough just stock (TBI & headers)? Not sure I need to be thinking about different pistons, rods, etc for strickly woods. Also, I run a Howell TBI (for a 360) on my 304. Will I need to get a different one for a 401?
Any opinions is appreciated!

[Dallas Lemon]

Reading this post really has me wanting a 401. Dallas like you, all I do is rock craw. :t: I run a 304 now (with a final drive of 99.9/1) in my scrambler and it runs fine but I guess I want MORE!!!! I like RPM's too! Your scaring a little on the 7000 #-o .
Is there a post that talks about taking a stock 401, doing some modifications (cam incl) to get the best low/midrange power possible? Is it powerful enough just stock (TBI & headers)? Not sure I need to be thinking about different pistons, rods, etc for strickly woods. Also, I run a Howell TBI (for a 360) on my 304. Will I need to get a different one for a 401?
Any opinions is appreciated!

My crawl ratio, like yours is deep at 115 to 1. With that ratio, a 5 HP Briggs and Straton will have plent of power! The reason I went with the 401 was I had it. The 360 I removed was running the Howell TBI, and I had to upgrade to the Holley Big Block Throttle Body. It is rated at 670 CFM, but I believe it flows more than that. When I ran the 401 with the 360 TB, it would fall on its face at 3600 RPM. The guy tuning the computer recognized the problem as the MAP sensor was leaning out the injectors. Install a bigger bore and all was good! Regarding the cam selection, I would not hesitate going to a 268 next time, or even the 272. The cubic inches alone insure good torque at the low end, especially with your crawl ratio. Going too radical may throw the computer into a bit of a tizzy if you start to affect the vacuum at idle. I don't think a 272 would be that radical, yet. My buddy with a 401 runs a dual pattern cam and gets along fine with it. He runs basically a stock setup with a Performer intake and the Holley 4DI TBI. It doesn't pull as well as mine, basically because of the heads. If you haven't figured it out by now, I REALLY like the Edelbrock heads! Go to Edelbrock's website and check out the information. There is also a thread on this site that discusses heads and the results of different head work.

[MoPedal]

Dallas-When I ran the 401 with the 360 TB, it would fall on its face at 3600 RPM.
The guy tuning the computer recognized the problem as the MAP sensor was leaning out the injectors. Install a bigger bore and all was good! My understanding is that Howell has chips avail for the 401 plus changing a few things on the TB. Was it just a personal preference to go with the Holly or does the Howell have problems fueling the 401?
Dallas- It doesn't pull as well as mine, basically because of the heads. If you haven't figured it out by now, I REALLY like the Edelbrock heads! Go to Edelbrock's website and check out the information. There is also a thread on this site that discusses heads and the results of different head work.
Went to the site, saw the heads, but I'm not really knowledgeable enough to see the difference between stock vs Edelbrock(other than the valve angle). There are a few things you never regret buying such as beadlocks, lockers, TBI, and others.....Edelbrock heads may be one of those things too! If possible, I need you guys help in deciding that.
Also, how critical are the oil modifications?
Again I appreciate all your help!

[jeepsr4ever]

Mopedal..first of all nice Jeep. I read the article on your jeep at Walmart of all places. :?:

Oiling mods are neccesary if your crawling or ramping up the R's. Some simple ones like higher capacity oil pans will fix the RPM issue most of the time but you need a swinging pickup for crawling. I have run out of pressure in my CJ many times before I started adding mods. We have a new swinging pickup for stock and deep sump pans that will save alot of motors coming out soona nd it may be something to check into. Do a little reading around the site..lots of great info.

[MoPedal]

I have looked at the AMC oiling and even I understood part of it but I had trouble getting a lot of the pictures to come up...they are just showing as red X's and I can't open them. I may not be doing something correct trying to pull them up....the pictures I did see were very good.

[Mudrat]

I have looked at the AMC oiling ... a lot of the pictures to come up...they are just showing as red X's
And you won't be abo\le to until they are re-hosted. We had a host change a while back and those pics MAYm not have been re-hosted when that all happend.

MC's gunna have to fix it - I don't have the pics. :smile:

'Rat

[MoPedal]

Thanks Rat, I thought I may be doing something wrong!

[Dallas Lemon]

"My understanding is that Howell has chips avail for the 401 plus changing a few things on the TB. Was it just a personal preference to go with the Holly or does the Howell have problems fueling the 401? "

I contacted Howell regarding the upgrade. What I was looking for was a 454 Throttle Body, but they are difficult to find. Howell uses the Holley on their big block applications, so I went with their reccomendation. And, yes they do have pre programmed chips to match your set up, but I have a local mechanic that installs an EPROM and burns it after tuning the computer.


"Went to the site, saw the heads, but I'm not really knowledgeable enough to see the difference between stock vs Edelbrock(other than the valve angle). There are a few things you never regret buying such as beadlocks, lockers, TBI, and others.....Edelbrock heads may be one of those things too! If possible, I need you guys help in deciding that."

When I took the 401 to the machine shop, I consulted with them about using the Edelbrock heads. He knew of no one that had installed a set on an AMC, and he would rather have seen me port the stock heads. I really cannot compare the Edelbrock heads to a set of ported and polished heads. But, the Edelbrock heads better flow characteristics. I don't mean to start a debate at all, but it was my personal choice to go with the heads rather than spend $1000 on head work. I also went with roller rockers, too.

[Dallas Lemon]

Check out this link. It has an excellent write up on heads, and results of the modifications performed.

http://www.amcforums.com/cgi-bin/yabb2/YaBB.pl?num=1116866495

[Dallas Lemon]

I'm honored that I have gone from a NEWBIE to a Cook. That's a good thing..............Right?

[Mudrat]

I'm honored that I have gone from a NEWBIE to a Cook. That's a good thing..............Right?
Yup .... a GOOD thing :!:

Pat

[MoPedal]

Thanks much Dallas, alot of info about heads there. Sounds like the 502's with different valves is the way to go if staying close to stock. Even if you go with Edelbrock they may be some changes to make. Good info! You've given me something to think about!
I have been known to float the valves a time or two...you recommend the roller rockers for woods use? How often will they need adjusting (assuming they are still solid lifter only)?
Many thanks for the info!

[Dallas Lemon]

"I have been known to float the valves a time or two...you recommend the roller rockers for woods use? How often will they need adjusting (assuming they are still solid lifter only)?
Many thanks for the info."

Actually, I am still using a hydraulic setup, just with the roller rockers. No adjusting required. Just set them up initially how the instructions say and forget about 'em.

[Holeshot]

hey, guys!!!

A STOCK '71 401 put out 430 ft/lbs of torque!!!

The heads are extremely RPM friendly & can flow well past 7000RPM, which the crank & rods are fine with.

An old-school build will net 500+HP & over 500 ft/lbs of torque.

Choking down a 401 with little cams, intakes, carbs, & headers may be OK for rock crawlers who want a 401, but for those who want to go fast, an old-school, musclecar build with 500+ HP at 6000~6500RPM STILL gives over 500 ft/lbs of torque from around 4000 to around 5500, that's with a "little" hydraulic .550" lift 292 DUR cam. This build STARTS with almost 400 ft/lbs of tq at 2k RPM!!! Another 30HP is available with 2.08/1.74 valves, maybe 50+ with a rad roller cam, & 30 with TotalSeal gapless rings. The bigger valves hurt the bottom end perf little due to the big, great flowing ports we started with, but choose your cam by what your REAL RPM range and other mods will be.

A good rbld with 10.2~1CR, 600CFM carb, 2 plane intake, small-tube headers, & a Comp 252H (LESS lift than stock!!!) should be around 580 ft/lbs @ 2000RPM & 340HP @ 4000RPM (SHIFT before your head hits the windshield!!!!!!).

A stock '70 360 with free-flowing exhaust puts out around 290 ft/lbs at 4k & 287hp at 6k, the 401 is almost double, as someone remarked. The 401 can really make use of those great heads.

I would like to see the dyno charts of someone building a rock-crawling 401 who tries the early '69 style heads. I have to believe that the little ports would give more tq at the low revs, as the '70 heads have very large ports that scream for revs.

Note that I DO use the Dyno 2000 program and have built most stock AM V8s in it & the number are close but for the head flow you choose should be "Canted Oval Port" as they are close to what the '70 heads flow. I have made flow files from flow charts and the numbers come out real close.

[zero cool]

hey, guys!!!

A STOCK '71 401 put out 430 ft/lbs of torque!!!

They changed the way they measured HP and Torque starting in 1972.

Before then, they used gross ratings. They would hook up the engine to a dyno, run the oil pump and water pump remotely, have no AC or power steering pump, attach open headers, put a velocity stack on the carb, etc. and then run the dyno.

Starting in 1972, the rules changed and they started using net horsepower ratings. You had to run the engine as it was installed in the vehicle. It had to have all the accessories hooked up (i.e. water pump, AC compressor, power steering pump, etc) as well as full factory exhaust and air filter.

That caused an across the board drop in horsepower/torque ratings of 20-40%. But it more accurately measured the true horsepower and torque being generated by the engine as it sat in your car.

[tarior]

Weren't the '70 and '71 360's rated at 395lb/ft torque and 290 hp? With the 401 having 430 lb/ft and 330 hp. Both were fairly conservative.

[Holeshot]

Those spex sound right.

As far as the way of measuring changing in '72 (SAE), correct. Joan Claybrook and the tree huggers had also gotten the CRs dropped a bunch along with retarded cam & ignition timing & smog controls plastered here, there & everywhere!!!

NOW we can start talking about 300HP 426 HEMIs & 427 Chevies!!!

Either way that makes you feel comfy.

My 390 AMX pushed out 518HP to the rear wheels, thru full exhaust, with all the accys running. That's with std hotrodding techniques & 9~1 CR.

[KJMac]

On the 360, planning to get a cheap FSJ without motor and swap in and sell the whole shebang to try and recoup cost.

I think the cam is hurting me. I am usu foot planted to hold 50-55 up to the tunnel. Motor is new. I've played with mix/timing for some time and improved power, but not lots. Ignition is already about as hot as it gets.

May install O2 sensor and tune carb more. Headers too. And may even try another cam. Hate to build a 401 without knowing what went wrong with the 360.

Higher CR is a must have as far as I can discern.

On the 80mph J-truck, what gearing, tire size, and cam? Thx.

MichaelWhat kind of timing curve are you running? I would look in to an HEI distibutor from mallory. Headers and dual 3" exhaust. If you don't do TBI than I would contact Sean Murphy ans have him build you a Quadrajet. A friend of my brother built a 401 for his Grand Wag. to pull his sleds up to the mountains. The build consisted of 9.5:1, stock heads,home ported. 270 Comp cam, Edel. performer intake poerted exhaust manifolds, single three inch with flowmaster. 3.08 gears, automatic. 32-11.50 tires. 272hp 368 torque at the rear wheels with edel. 750 carb and Mallry ignition.

[KJMac]

Thanks for the responses so far! The advice is VERY valuable.

The reason I didn't want to change anything but motor is I just spent $1800 on rebuilt, locked and regeared axles. Now I'm married and spending $ is... limited. :)

I wanted to keep hwy rpms to stock level. A mistake? Maybe. But get this...

A friend has an 87 GW, 33" tires, 4" lift, roof rack, very similar to me, but runs 3.31 gears and a 401 with 10:1 CR and mild/stock cam plus a Quadrajet which he just got dialed in a few weeks ago. He is now running 3/4 throttle in 3rd up that first big hill on 285 to keep up with traffic running 60-65. He runs most passes in 3rd. I've personally seen this truck PULL AWAY RAPIDLY from me on hills where I am foot to the floor to hold 55-60 in 3rd with only modest accel in 2nd. On Monarch Pass I was in 2nd where I could accelerate ok but he STILL pulled away quickly (I think he was in 2nd too). I've also seen him accelerate from 65 to 100 on nearly flat ground where I could barely make it to 80 in the same timeframe. Frankly it is jaw-dropping to see.

So, that is what is possible. Btw, Spitfire built his motor.

I've been playing with Desktop Dyno a lot (just ordered the 2000 vers). I modeled my motor and his as best I could. What I've found is my Comp Cams 260H is a horrible choice with stock CR and exhaust, weak on torque in just the rpm band I most use. He has like 100 lbs-ft on me with his combo.

In a 401 with 9.5:1 CR, small tube headers, the Edelbrock Performer cam puts out 430+ lbs-ft in 2000-3500 range, and with 320 hp @ 4000 (best of 260-ish cams). Factory Pontiac grind specs I found on the web puts out 440+ lbs-ft from 2000-3000 (447 @ 2500, 'only' 435 @ 3500 and 408 @ 4000) with slightly less hp @ 4000 (311 vs. 320). No other cam comes close to these two in torque. The next best are down 10-20 lbs-ft 2000-3000.

Seems the Pontiac grind puts peak torque @ my cruise rpm, most torque in the power band, and peaks hp @ 4000 suggesting good off-idle torque. I doubt 9 hp matters since it'll be 30 more than I have now. I think it's the best choice I've got. That's what I am leaning towards.

But this is all cloud pushing based on a lot of assumptions, book learning, and junk. What are your thoughts?

Also, EFI is planned too.

Michael Is there AMC engines on the Desk top dyno 2000?

[Mudrat]

Is there AMC engines on the Desk top dyno 2000?[/quote]
In my version - only if you build it ... :smile:

Pat
Still in the UK

[Holeshot]

I have to ask, why take a great breathing engine & choke it down with lil cams, carbs, & exhaust?

The 401 will easily put out 550 HP & 550+ ft/lbs below 6500 RPM with std hotrodding techniques. I think the tq peak is around 3000 or 3500. PLEASE don't choke it down!!! It's not like a Chevy or Ford or whatever. Those heads flow GREAT and 10-1 compression should be fine with pump gas as long as you have it tuned correctly. Take a look at the 292H for a much better Comp cam, although they grind their cams too similar to their SBCs cams, and offer little in dual-pattern cams.

You actually have to build your 401 choked down to get less than around 430 ft/lbs of torque. And then you are wasting those great ports when they need to breathe.

I am assuming that you want power, of course. If a guy wants to put around on trails, he could use an inline six.

As far as I'm concerned, all that naysaying advice about using little cams carbs & exhaust is strictly for rock crawlers or trail riders. The 70 and up AMC heads turn out to be some of the best passenger car heads and make the AM V8s some of the most responsive engines to build, if you don't starve them. A stout 360 can use every bit of 850CFM, for instance. AMC even sold HiPo Holley 3bbl carbs up to 900CFM to go on top of the Edelbrock R4Bs they were also selling at their dealerships.

If you want to peak your HP at 4000 RPM, you are not even getting into the powerband that the heads were designed for. Like shifting a 125 motocrosser at 4000 RPM - ICK!!!! I think the STOCK cam HP peaked at 4600 or so, you are going the wrong way!!! Less RPM = less power!!!

Those Performer numbers you quoted are no better than a stock 70s 401.

The 401 can go to 6500 safely with ease, and is completely safe there so long as it is a sound engine. I would definately suggest spending the extra few bucks for forged pistons, and get them with 1/16" compression rings, TotalSeal gapless rings being worth 30~50 cheap HP, especially over time. Set your piston to head clearance at .045" to eliminate ping and have the heads "open-chambered" and you should end up with ten to eleven to one CR.

I have TONS of AMC cam, head, & "*.dyn" files for Dyno2000. (1800HP twin turbo anyone???)

OH YEAH: Another COOL thing about Dyno2000 is that the "*.dyn" files that it generates can be directly imported into other programs, such as "DeskTopDragStrip" and "DragStripPlus" so you can actually sim the 1/4 mile. PLUS you can import the dyn files into Bethesda Software's "HotRod Magazine's Championship Drag Racing - Burnout: Player's Choice Edition" and "NIRA Drag Racing". "PCE" (as it is called) came with a hunter green '69 AMX, so I have mine painted up just like my BigBadOrange with black stripes. If I put a stock 390 in it, it runs low 14s. When I simmed my 518HP 390, it ran low 11s in the low 120s in street trim, just like my car!!! With traction it goes hi 9s/lo 10s, just as you would expect. Extremely cool. Back when the sim was current, we would race all night on line & sanctioning bodies were popping up everywhere. Really came up with some QUICK setups!!!

The sim went the way of 3DFX, but I did keep my old Pentium 200MMX w/VooDoo3 just to run that sim. Of course, I couldn't resist painting an SS/AMX!!![/b]

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