i hate asking what i am about to, search just turned up a few what if's, but i am wanting to choose the right parts the first time, and get it right so i wont have to redo somthing...

i am putting together a 355, 4340 forged eagle crank, h beams, but now i have to decide on what pistons to run, i found these for 350,

350 CHEVY REVERSE DOME PISTONS 23 DEGREE -2618 ALLOY

LUNATI PART #131AJ5S3
23 DEGREE VALVE ANGLE
-20CC REVERSE DOME
2.500 X .927" 141.9 GMS WRIST PINS
1/16 X 1/16 X 3/16 RING GROOVES
SPIRAL LOCKS INCLUDED
360 DEGREE SKIRT DESIGN
4.030 BORE
1.550 COMP HEIGHT
WORKS WITH THE FOLLOWING COMBINATIONS

STROKE ROD DECK
3.480 5.700 8.990
3.500 5.700 9.000

but i want to get the compression around 9.0:1, i will be running 195 eliminators, with a stealthram, cam is still in the air also, looking at the comp xfi series closely, nothing but top dollar stuff going in, i will be adding a procharger later this year, probably a d1sc with intercooler.

i know people say 8:1 to 8.5:1 but i am worried about thermal effecincey also.

any help with this and a cam selection is appreciated highly, i am just afraid the guys at comp will lead me the wrong way, btw people are saying as of late..

thanks everyone

adam

 

You didn't mention which cc size of eliminators you were looking at.
With the relatively large 195cc heads, you can go to a decently large size cam. Especially with your 4.56 gears and T56.

No, you don't want 9:1 CR. That just means you can't run as much boost. I wouldn't worry too much about thermal efficiecy, that only really makes sense NA. Going from 8:1 to 9:1 will net you maybe 10% more power, looking at it VERY optimistically. So about 40hp maybe.
Or it means losing that 40hp, and gaining the ability to run ~6psi more boost, or 150HP at least. Yea, i'd rather have the boost too. There's a reason everyone else does low CR with a blower - be like everyone else!

I think the big 76cc pistons will net you a nice dismally low CR. Those pistons should work nice, they're forged and all that. I know speed-pro makes a nice forged blower piston that's probably a bunch cheaper. Big dish on it.

 

well i can get those pistons for 350 brand new, i don't see speedpros being much cheaper, but i will look into it.

it's funny, the piston mentioned above doesen't come with compression ratio est per cc head like most does, i might just go ahead and get some srp's or je, no reason to start skimping now, i will probably regret it in the long run...

with a large size cam you spoke of, do you have any possible reccomend dur @.050 figures, to help a man get into the general ballpark?

i was looking at the biggest xfi comp cam, but i want to be sure of it....

again thank you for the responce and any more help is most defanantly appreciated!

thanks!

adam

 

I think the speedpros are closer to $250. I know they are cheaper than the "racing" name pistons. I (personally) don't think there's a big quality difference in pistons, as long as the rotating assembly is balanced, and you're not worried about having pistons a few grams heavier (if under 7000RPM you probably won't need to worry about it), then i'd save the cash and not get the slick stickers. Pistons don't add HP for me so...

I was invisioning something like a high 230*, low 240* on the intake. Depends on how you want it to drive, if you mind the lope, etc. High LSA since you're using injection. The blower, and long LSA will tame the cam like crazy. With those insanely steep gears, and the stick shift, and the good heads you have absolutely no reason to go small on the cam. Go nuts!

 

well, iv'e decided on the xfi 292 cam, but the compression ratio is driving me nuts....


from what i have read everyone running a procharger can't seem to get the psi they are shooting for with the belts they have, cause of slippage

so my new question is, why try and shoot for a higher psi like 12+psi if belt slippage is going to keep me under that, wouldn't a lower compression ratio kinda be redundant if the procharger can't give me the boost i need for the lower compression?

 

Yes, you're right. I think you should tackle the problem at hand rather than avoiding it though - fix the belt issue.

I think 12psi is probably all it'd take anyway, even with 8:1 CR, unless you're willing to run race fuel.