I have an 89' iroc with a 350. I know the stock compression ratio is 9.3:1. How thin do I need to go to get a ratio of 9.8:1?

 

JDM,

You probably won't be able to raise compression that much with only a gasket change. You'll have to eliminate about 5-7 CCs of free space from the chambers to accomplish that, and a gasket might get you one or two CCs at best, unless you go dangerously thin or use solid metal gaskets (seldom good on a street engine).

The stock gasket should have a compressed thickness of 0.039"

------------------
Later,
Vader
------------------
"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

i think the shim gasket is .015 or so. not much differance adn you need a good finish on the deck and head to get them to seal. if you're going to have the heads off get them resurfaced. that should cut .010 off of them, or milled.

------------------
ICON Motorsports
1st & 3rd

 

I don't know about stock L98's but on the ZZ4 the composite head gasket can be replaced by Fel-Pro PN 1010 9CC's compressed volume. That will bump the ZZ4 from 10 to 10.5 CR. Fel-Pro 1010 is probably worth about a .5 CR increase on any thirdgen.

------------------
84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

91 Firebird 5.0L TBI

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

Didn't GM use a thinner gasket on the 91-92 L98s? I believe I read that is how they upped the compression to 9.75 at the time.