Aluminum heads + iron head pistons =12:1?

[Flipper_1938]

I was surfing the web for cams today and found an interesting one. Anybody tried it?

A while back there was a post about swapping aluminum heads onto a camaro 3.4 and the result was a 12:1 compression or something like that. Has anybody actually done this. What kind of valve clearance does it have? Can this cam be run with this combo without having pistons fly-cut for valve clearance.

Any guesstimates what HP would come from this set-up?

At a glamce it looks like it would be fun.

Oh yeah, the cam is a Crane solid lifter cam.

Part Number: 251241 Grind Number: F-248/3334-2-12
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1980 1996 CHEVROLET 6 ROUGH IDLE, PERFORMANCE USAGE, GOOD MID AND UPPER RPM TORQUE AND HP, 3800-4200 CRUISE RPM, 10.5 TO 12.0 COMPRESSION RATIO ADVISED. BASIC RPM 3800-7200
Engine Size Configuration
2.8-3.1 L V

Valve Setting: Intake .022 Exhaust .022 HOT

Lift: Intake @Cam 3334 @Valve 500 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 3468 @Valve 520
Rocker Arm Ratio 1.5

Cam Timing: TAPPET @.014
Lift: Opens Closes ADV Duration
Intake 43 BTDC 87 ABDC 310 °
Exhaust 92 BBDC 48 ATDC 320 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99838
Loads Closed 110 LBS @ 1.688 or 1 11/16
Open 322 LBS @ 1.215
Recommended RPM range with matching components
Minimum RPM 3800
Maximum RPM 7200
Valve Float 8000

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 17 BTDC 51 ABDC 107 248 °
Exhaust 66 BBDC 12 ATDC 117 258 °

Remarks:

[94Camaro]

RE: Aluminum heads + iron head pistons =12:1?

if you use the aluminum heads + iron head pistons you end up with 14.2:1 CR. or something like taht. not advisable.

[Ortie666]

just givver man, get them and try, whats the worst that happens, u have a spare set of aluminum heads.. then that gives u time to time to get nutty with them, ohh ya, u ymm prolly wanna hange the intake manafold and all that jazz to have it fit, and dont be suprized if u have to run racefuel to drive to work... the desktop dyno clames somthin like 150hp/185hp... but id say givver it always could be a bit more.. never know unless u try

[Guest]

I am guessing this is with a 3X00

My calculations have put it anywhere form 11.6: all the way to about 12.2:1.

It will depend on deck height, and how thick of a gasket you run, as well as the CC of the chamber.

Chamber is around 28 cc from what I have heard so go +/- 1 on that. The piston for the iron head 3.1 or 3.4 has a 12 cc dish to it. Gasket thickness will be .060 or abouts but I use that.

I have contemplated using that cam or one milder with my engine setup. That should work in a gen 3 block no prob but not so well in a gen 1 or 2 block as it doesnt' haev the prioirty feeds. With use of the mechanical roller lifters in my aluminum block. Output with a gen 3 intake should be around 220 hp or so if I had to guess with a good tune.

That 155 hp is lame o andincorrect. It will do way moer then that.

I say go for it. You can run 93 octane with it on a good tune as well.

[SappySE107]

People have ran this setup on pump gas. Its the flathead pistons that would go way over 12:1, but the slight dished pistons are in the 12:1 area. If its 12ccs, thats quite a bit less than the stock 3100 piston. I measured them in another thread and I think it was around 29ccs.

[Ortie666]

well the 155 is with manafolds and mufflers, and as for the 12:1 at 93 octane ya, it prolly would work, not great tho.. id still use a race gas mix.. or lotta octaine booster( thats not always good, kuss the more time it takes to burn the more time somthing can go wrong), but that also depends on how new the pistons are and whatnot.. i supose once again the olny way to really know forsure is juss try it..

[SappySE107]

Depends on your cam, but iv seem 12:1 on 87 octane and 89 octane with 0 kr.

[Ortie666]

ya, i supose on how much fuel&air is aloud too go in plays a big factor...

[Kreb]

I don't know the ins and outs, but am fairly sure that you'll need custom length pushrods as well. Here's a site with a lot of info about about this particular combination:

http://www.domesticcrew.com/

[93camaro_zzz]

The piston dish on the iron headed GEN1 3.4 is actually 8cc, and the gasket thickness is 0.060, the aluminum head size is actualy 26.4, when I entered my numbers, after running through dilemnas with the deck height, I got 12.86:1. I got this same answer, on two different formulas. Thats a little high for pump gas. But it would be interesting. And also, where have you seen 12:1 on 87 and no KR? I would like to know.

[SappySE107]

The aluminum head is not 26.4. Maybe gen 2 but not gen 3. Its 28.4 with stock valves. And yes, it works on pump gas without issue as long as you tune the computer. You don't even have to kill all the spark advance. I wouldn't tell you it can run on midgrade with tuning if it took a lot of retard to get it to do that fine. On premium, its happy as hell. Where did I see it on 87 octane? 88 (or was it 89) cutlass supreme 3100 swap with headers and a cam regrind along with those pistons. I tuned the setup and it was fine on 87. No port work done at all.

[Guest]

someone here cc'd a iron head 3.4 piston and the dish was 12cc. Who was that? I remmeber reading it.