which cometic head gasket and why?

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Apr 3, 2012 | 09:09 PM

poltergeist 02

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which cometic head gasket and why?

I'm getting ready to order head gaskets and I'm trying to figure out which cometics to use with my set up. There seem to be many options cometic offers for an LS1. Which gasket would yield the best performance gains?

This is what i have:

stock bottom ls1
comp 228/230 .571/.573 112lsa (intake 71* abdc)
ported unmilled 799 heads with stock valves

cometic gaskets:
part# / compressed thickness

C5475-040 (.040")
C5475-036 (.036")
C5475-030 (.030")
C5475-027 (.027")

Last edited by poltergeist 02; Apr 4, 2012 at 07:12 AM.

Apr 4, 2012 | 06:11 PM

poltergeist 02

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any advise?

Apr 4, 2012 | 06:24 PM

baxsom

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From: Rockledge FL

the only thing i know about the cometics is that they are not as forgiving as the oem MLS gaskets about the sealing surface. from what i have been told both the block and heads have to be perfect.

Apr 4, 2012 | 08:33 PM

batboy

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I would not go thinner than .040" due to reduced quench clearances and due to the thinner you go the harder they are to seal. Personally, I like the GM MLS gaskets.

Last edited by batboy; Apr 4, 2012 at 08:42 PM.

Apr 5, 2012 | 01:03 AM

SmithS87

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I had the same question. Actually, I registered specifically to say to ask this question..

So, any advise will be so much appreciated

Apr 5, 2012 | 01:21 AM

gectek

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.040 or .045 for me. Also depends on how much the piston sticks out of the hole.

I would use a 3.910 or so head gasket to keep the quench higher also.

Apr 5, 2012 | 05:05 AM

ausls1

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With stock pistons id use the .040" gaskets, i'm using a .027" cometics gaskets but iv also got -8cc dish pistons, if had a smaller dish piston would've used a .040" myself.

Last edited by ausls1; Apr 5, 2012 at 08:06 AM.

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Apr 5, 2012 | 06:07 AM

mark21742

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From: PA/MD

I'd also use the .040". On average your piston sits around .005" up out of the hole so that would give you a .035 quench..035-.030 is optimum, when you get tighter there are gains, but as the metal stretches and expands it leaves less room for error.