53RUSSELL

iTrader: (9)

O.k. guys I’m tiring to decide on what piston go with. I'm rebuilding 2000 c5 ls1.
I have set stock 853 heads. I tiring to decide on witch way I want to go. I can go with stock 853 (66.67cc) heads and -11cc piston or having the bigger chamber 317 (71.06cc) heads and go with -4 flat tops piston. Witch is better combo for boost? Thanks for your help Guys.

GMCtrk

iTrader: (27)

My personal opinion is 317s - much better flow means less restriction and more power.

53RUSSELL

iTrader: (9)

853
intake port volume 200cc and exhaust port volume 70cc

317
intake port volume 210cc and exhaust port volume 75cc
On boost is going to make that much more power with the intake (10cc) and exhaust (5cc) more?

GMCtrk

iTrader: (27)

the 317 flows about 30 CFM more up top.

Low_LSX

iTrader: (33)

Everything you need to know about stock heads:
https://www.performancetrucks.net/fo...d.php?t=434396

zippy

Chosing the right piston is alot like chosing the right camshaft. What are your goals with the new shortblock? What boost levels are you honestly going to run. Not an un-realistic number either like many shoot for. If your goal is 8-12psi you'll want compression between 9.8:1 and 10.5:1. With good fuel you could run that compression to 20psi on a whim, but your everyday boost level is your concern. If you are looking to do 15-20psi on a regular basis you'll want to be between 9.3:1 and 10:1. At 20+psi you'll want 8.5:1 to 9.5:1 or so. There are also differences in materials. For example if you want to run up to 15psi of boost with no nitrous in a daily driver type application you'll want to run a 4032 alloy. For an application where you'll be squeezing every last degree of timing to it with 15psi of boost or more and possibly nitrous you'd want a 2618 alloy. A 2618 alloy is a stronger alloy, but often makes more noise (especially on cold starts) and can be more susceptible to oil consumption issue's

As for the choice on the cylinder heads of the two you have, I'd take the 317's any day over the 853's. You'd be better off with 243's though for a street application as the 317's will really knock your compression down even with a -4cc flat top piston.

53RUSSELL

iTrader: (9)

O.k. Zippy look at running around 10 to 15lb of boost on the street. I'm currently running 10lb on my stock 5.3. I would think my mpt70 would maxout @12 to 15lb of boost. I got free set iron 373 yesterday witch has same specs as the 317. From my calc I should be around 9.5 with -4cc piston.

00Silv4.8

iTrader: (10)

241s and 243s are pretty similar, a .4 more compression and 10cc's on the intake and 5cc's on the exhaust.

AJ gave the best thread. On my old comp I had a link with actual dyno tests (same set up, car, everything) with 241s 243s 317s and I wanna say with an LQ9 as well with the 317s. And even intake variances (how small they are). Wish I still had it.

Aaron, I gave my opinion the other day when we talked, to be honest, if you want the little more compression (and money in your pocket) keep your heads. You will spool boost a little quicker but are you gonna loose any on the top end?
Then the 317s your gonna loose some comp, so more lag and are you gonna loose or gain any on the top end? Your discretion, I know your already gonna have to drop a bucket of money on just getting the block square. My opinion would be just rock the 853s, you can always do a head swap later if you dont like em

53RUSSELL

iTrader: (9)

Well end up going with forgen flat top probe pistions. I would like to know where you get head gasket thinkness less than 0.050. Thanks for the help.