High Compression with boost

[fifesjeep]

I can almost put my hands on a turbo that will give me 6-8lbs of boost... The only thing that has my on the fence is that my current set-up is running 10.5:1... I'd like to toss in some SS valves, 2.080 Int 1.74 Exh. and some hardened valve seats. If I toss this turbo on I imagine I would have to get the 360 ringed so that it will handle the pressures... So with what, would be a good cam selection... I'm thinking something in the range of .688" Int and .702" Exh... I have The Harland Sharp 1.7:1 Roller Rockers and I'll be tossing on the Torker Intake and on top of that a 750 Proseries carb... I'm sure I'll have to step up in header size from 1 5/8" to 1 3/4"... As you can see/read I am in the beginning phase (IDEAS)... I'm scratching for ideas... or experiences in this rhelm of building an AMC for screaming power... (Street).

[tufcj]

My suggestion would be to build another motor. Typical boosted motors are in the 8:1 range, even less with more boost.

With 10:1 compression, I think you'll get a ping with any boost and any grade of gas. Using a long overlap to hold both valves open will kind of defeat the purpose of the compression or compressor.

I'm sure others with more experience with hairdryers will chime in.

Bob
tufcj

[fifesjeep]

basically the same thign my buddy said...
he's been telling me to go with a stock 401 do a little top work... ie: intake, carb, head, exhaust and toss on a turbo or two...
I'm not sure that I'll be able to rip apart the 401... lol

[ironman_gq]

throw in some low comp pistons and get a set of good head gaskets and see what happens :lo1l: IF it blows up #-o :smile: :lo1l: build another one. or get a stock 360 (they're everywhere and cheap) and build a boost motor and giver her hell :lo1l:

[fifesjeep]

I think I am going to play around with the 401 (currently in the 1980 CJ-7)... If I can grab 2 turbos from Evil Bay then it looks like I'll have a decent summer project that my ol' lady will hate me over... :razz: :?

[ironman_gq]

as long as its your money and not hers she shouldnt have anything to complain about 8) if she starts on about money tell her to go get a job or a better job whichever the case may be :(:

[jeepsr4ever]

We are doing a 401 blower motor buildup very soon here that will have a 7.5-7.7 to 1 compression ratio. When you add a blower and your at 8.5 on up you will have to limit the amount of boost or you will detonate. On a blower motor even the crankshaft tolerances are opened up and the rod side clearance. There is alot to consider when building a blower motor. There are some good sites to check out and people to talk with as far as what you will need for the lower end.

[dbesade]

I can almost put my hands on a turbo that will give me 6-8lbs of boost... The only thing that has my on the fence is that my current set-up is running 10.5:1... I'd like to toss in some SS valves, 2.080 Int 1.74 Exh. and some hardened valve seats. If I toss this turbo on I imagine I would have to get the 360 ringed so that it will handle the pressures... So with what, would be a good cam selection... I'm thinking something in the range of .688" Int and .702" Exh... I have The Harland Sharp 1.7:1 Roller Rockers and I'll be tossing on the Torker Intake and on top of that a 750 Proseries carb... I'm sure I'll have to step up in header size from 1 5/8" to 1 3/4"... As you can see/read I am in the beginning phase (IDEAS)... I'm scratching for ideas... or experiences in this rhelm of building an AMC for screaming power... (Street).

I'm not familiar with building boosted AMC Blocks but I am familiar with Boosted engines. What turbo(s) are you looking at using? What is the volumetric efficiency of the turbo at 6 to 8 PSI? A Small turbo will spool very quickly on a V8.

In all reality I have a similar idea of using SRT4 Turbo's on my 304 while dropping the compression ratio to 8.1:1 and pushing 10lbs of boost or so. Shouldn't need to ring the head but definitely use some better rods and pistons as the EGT's will melt the stock stuff even at 6 to 8 PSI. I would definitely use some better valves in the head and find a nice turbo profiled cam for this setup (Crower makes some interesting cams for the SRT4 so I'm sure they could custom grind something for the AMC Stuff) but there are other Cam makers out there with turbo grinds for AMC.

Good luck, make sure to intercool the setup and get the loudest friggin BOV you can.

-Dave

[fifesjeep]

Thank Jeepsr4ever & dbesade... Like I said in the original post I am looking for ideas and thoughts... Basically to see what will pan out in the end... So far what I've been reading and what you guys have said basically reduced the chances of me doing this build.
My buddy said he'll sell me a T3 for $200... But he also said that If I wait chances are I can find deal on evil bay... He has a twin turbo 350... I'll get him to send me some pics and specs of his motor... it looks nice... lol :?

[dbesade]

Thank Jeepsr4ever & dbesade... Like I said in the original post I am looking for ideas and thoughts... Basically to see what will pan out in the end... So far what I've been reading and what you guys have said basically reduced the chances of me doing this build.
My buddy said he'll sell me a T3 for $200... But he also said that If I wait chances are I can find deal on evil bay... He has a twin turbo 350... I'll get him to send me some pics and specs of his motor... it looks nice... lol :?

If price is a concern, look for 2 SRT4 Turbo-folds (Turbo and Manifold) I am thinking about sending on to MC to see if he can make an adapter plate for them. The turbofolds sell for around $120 and contain the Manifold, Turbo, and Wastegate Actuator.

-Dave

[fifesjeep]

dbesade... I'll have to google and rack the brain... thanks for the help.

[kiwi]

Try this for size, I have a bone stock 78-401 ($100 for the whole wagoneer) I put a used turbo off a 97 powerstroke ford on the thing, piped the exhaust from the 401 manifolds to the twin inlets on the turbo. Modified a used Holley, built a carb hat from an old kitchen pot I got from the thrift store (didn't keep the handle) welded in an exhaust 90 & hooked it up to the turbo with a piece of hose & a cheap ebay BOV. The BOV keeps the boost to 11lb up to 5500rpm, beyond that it's too small & crushed a float in the carb. Just need to double up the BOV's, cheaper & easier than a waste gate. The boost comes on strong at 1500rpm & I have a stock converter in the trans. It's a blast to drive & it's cheap.
Cost:-
$100 = 401 engine. (I got the whole wagoneer for that).
$100 = Junkyard turbo 97 Powerstroke. (I got the mount base, the two exhaust rings & plates, the turbo front pipe & v clamp & the short intake pipe & v clamp that feeds the eng.
$29 = blow off valve. (ebay)
$100= Exhaust U bends, oil lines & fittings & misc.
$0.25c= Pot. (steel, even had flowers on it)
That's pretty much it, I dont know what hp it makes but in a 1700lb street rod, shittin n gittin comes to mind & I've never had a passenger that hasn't come out with a few holy $#!:<'s.
I'm sure it would work on a late smog 360 but would come on a little later. If any one wants to give it a shot they will not be dissapointed. A low cost AMC to kick some Big 3 butt.
Kiwi Sid.

[dbesade]

Try this for size, I have a bone stock 78-401 ($100 for the whole wagoneer) I put a used turbo off a 97 powerstroke ford on the thing, piped the exhaust from the 401 manifolds to the twin inlets on the turbo. Modified a used Holley, built a carb hat from an old kitchen pot I got from the thrift store (didn't keep the handle) welded in an exhaust 90 & hooked it up to the turbo with a piece of hose & a cheap ebay BOV. The BOV keeps the boost to 11lb up to 5500rpm, beyond that it's too small & crushed a float in the carb. Just need to double up the BOV's, cheaper & easier than a waste gate. The boost comes on strong at 1500rpm & I have a stock converter in the trans. It's a blast to drive & it's cheap.
Cost:-
$100 = 401 engine. (I got the whole wagoneer for that).
$100 = Junkyard turbo 97 Powerstroke. (I got the mount base, the two exhaust rings & plates, the turbo front pipe & v clamp & the short intake pipe & v clamp that feeds the eng.
$29 = blow off valve. (ebay)
$100= Exhaust U bends, oil lines & fittings & misc.
$0.25c= Pot. (steel, even had flowers on it)
That's pretty much it, I dont know what hp it makes but in a 1700lb street rod, shittin n gittin comes to mind & I've never had a passenger that hasn't come out with a few holy $#!:<'s.
I'm sure it would work on a late smog 360 but would come on a little later. If any one wants to give it a shot they will not be dissapointed. A low cost AMC to kick some Big 3 butt.
Kiwi Sid.

Kiwi,

I have a few issues with what you wrote. A BOV (Blow off Valve) only activates when the throttle plate closes and the boost pressure bounces off it back towards the turbo and causes compressor surge.

What you just wrote is a load of crap (in regards to the function of a BOV). A BOV IS NOT A WASTEGATE AND YOU CANNOT REGULATE BOOST PRESSURE ON THE COMPRESSOR SIDE WITH A BOV. A BOV IS SIMPLY THERE TO PREVENT COMPRESSOR SURGE.

What you need is a WASTEGATE ... WHICH OPENS UP A PORT EITHER IN THE MANIFOLD OR IN THE TURBO TO BYPASS THE COMPRESSOR TURBINE THUS CAUSING THE EXHAUST GASES TO BYPASS THE TURBO AND LOWERING BOOST PRESSURE AND REGULATING IT TO YOUR DEFINED MAX.

Sorry if I come off like an ass but that kind of information is what blows motors up. I have pushed over 20 Lbs on a 3bar MAP sensor and custom tuning ... realize that fifesjeep is only looking to push moderate boost (5 to 7 lbs) as a 360 has a cast crank that will only deal with so much and the volumetric efficiency of a turbo will make all the difference. I don't want anyone to blow up their hard work is all.

I think you may have some vocabulary mixed up and some definitions wrong and that may be the cause of the mixup. Kiwi I always admired your turbo build and its what made me want to boost my rig so please don't take my post as me diggin on you. I ripped my foot open so I'm in a lotta pain today so i'm a bit grumpy.


#-o #-o

-Dave

[kiwi]

Sorry to hear about your foot Dave, some times we get things where they shouldnt be. Your theory is all totaly correct, but I've been working around this race car theory crap now for 40yrs & it's not all set in stone. The BOV is opened two ways, the top side is by vacuum & is hooked up down stream from the carb & when the manifold see's vacuum it opens the BOV. I dont hook that side up. The bottom side is the boost side & I hook that to the carb hat & the valve is set to 10lb. The fact that the compressor is not feeding everything to the turbine, that keeps the turbo speed down until 5500rpm when the cfm becomes too much for the BOV to handle & the boost starts to climb. More BOV cfm rating will solve that. If you yank your foot out of the throttle at 5500, the BOV barks pretty hard but doesn't back spin the turbo. I tend to back out of the pedal, not side step it. The only way I could hurt this thing would be to disregard the tach or the boost gauge, but I did crush the secondary float in the carb before I got it all dialed in & have since changed to Nitrofil (solid) floats.
I built this car to be the push car for my 250mph Dodge Conquest I run at Bonneville. That's also an unusual low buck turbo car. 2.6L block & head with 2.3L 4d55 diesel crank rods & pistons. The turbo is off a Detroit 8v92 2stroke diesel of
732cu in, rated at 134 lbs/min & makes 62lb through two 3ft ice water aftercoolers inside the car to a home built Hilborn- style fuel injection & fired by an Electromotive 4 coil crank trigger ignition. Only ran 217mph last yr in the 2nd mile in 3rd gear when the trans unloaded its self into the safety blanket.
You'd probably find that one a little different as well.
Gail Banks checked it out at Bonneville & was surprised how simple it is & how well it worked. The AMC didn't surprise him at all, He liked it as a low buck low boost blow through system.
It does really work quite well. Kiwi Sid.

[dbesade]

Sorry to hear about your foot Dave, some times we get things where they shouldnt be. Your theory is all totaly correct, but I've been working around this race car theory crap now for 40yrs & it's not all set in stone. The BOV is opened two ways, the top side is by vacuum & is hooked up down stream from the carb & when the manifold see's vacuum it opens the BOV. I dont hook that side up. The bottom side is the boost side & I hook that to the carb hat & the valve is set to 10lb. The fact that the compressor is not feeding everything to the turbine, that keeps the turbo speed down until 5500rpm when the cfm becomes too much for the BOV to handle & the boost starts to climb. More BOV cfm rating will solve that. If you yank your foot out of the throttle at 5500, the BOV barks pretty hard but doesn't back spin the turbo. I tend to back out of the pedal, not side step it. The only way I could hurt this thing would be to disregard the tach or the boost gauge, but I did crush the secondary float in the carb before I got it all dialed in & have since changed to Nitrofil (solid) floats.
I built this car to be the push car for my 250mph Dodge Conquest I run at Bonneville. That's also an unusual low buck turbo car. 2.6L block & head with 2.3L 4d55 diesel crank rods & pistons. The turbo is off a Detroit 8v92 2stroke diesel of
732cu in, rated at 134 lbs/min & makes 62lb through two 3ft ice water aftercoolers inside the car to a home built Hilborn- style fuel injection & fired by an Electromotive 4 coil crank trigger ignition. Only ran 217mph last yr in the 2nd mile in 3rd gear when the trans unloaded its self into the safety blanket.
You'd probably find that one a little different as well.
Gail Banks checked it out at Bonneville & was surprised how simple it is & how well it worked. The AMC didn't surprise him at all, He liked it as a low buck low boost blow through system.
It does really work quite well. Kiwi Sid.

Kiwi ,

I am simply floored by that logic :D. I'm impressed, you are completely correct. Interesting way to set it up but it works. I'm more of a MPFI Guy myself when it comes to boost. The turbo your using should be fairly immune to compressor surge anyways simply due to its size. Does your backing out of the pedal cause much compressor surge or does the way you have the intake plumbing (with the carb change that idea?).

With my SRT obviously I have a throttle body and when you let off the throttle partially it creates compressor surge due to SOME of the Boost Pressure bouncing off the partially closed throttle plate and the BOV doesn't always sense vacuum right away. Then again Compressor Surge in this manner is more of a smaller turbo issue.

Always goes to show ya you can learn something new if your open to it. Thanks for your reply and looking forward to your response.

-Dave

P.S. I took some pain meds some I'm a bit more cordial now :razz:

[xracer390]

We are doing a 401 blower motor buildup very soon here that will have a 7.5-7.7 to 1 compression ratio. When you add a blower and your at 8.5 on up you will have to limit the amount of boost or you will detonate. On a blower motor even the crankshaft tolerances are opened up and the rod side clearance. There is alot to consider when building a blower motor. There are some good sites to check out and people to talk with as far as what you will need for the lower end.
Soon, soon, how soon ? =D> I am in desperate need of some good news.........very desperate.......things are not going well over here MC :smile: