Static CR

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Dec 3, 2007 | 02:02 AM

thirdtimevetteowner

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From: Rochester PA

Static CR

I need help computing my static CR on my '89 L98. I am going with the new 195 cc AFR Street Eliminater heads, and having AFR angle mill them to 56cc (that's the most they will mill them). They will be going on my stock block (44k), using GM's .028" (5.8cc) compressed thickness head gasket for a 4.00" bore (unless someone knows of a thinner one). My objective is obviously to up my CR as much as possible, w/out having to pull the engine down for flat tops. Anyone have the formula to figure it out? BTW, I did a search and came up with nothing. Any help would be much appreciated.

Dec 3, 2007 | 06:14 AM

Z51L9889

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From: Centerville OH

I come up with 10.26:1 using a stock deck height and a -10 cc piston dish volume. I don't know the exact volume for the stock pistons, but this is in the general neighborhood.

Dec 3, 2007 | 08:33 AM

AGENT 86

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From: Summerland B.C. Canada

Dec 3, 2007 | 08:43 AM

dan0617

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From: Tyrone PA

http://members.cisdi.com/~anesthes/comp.html

That is the compression ratio calculator I use. Thanks anesthes! Also, you can go with a steel shim headgasket coated on both sides. Fel pro makes one that is .015 compressed. I am considering that myself when I swap heads in a few weeks. I am also considering the Mr. Gasket Ultra Seal gasket that is .028 but don't know if they are any good or not. Summit has a nice selection of gaskets.

Dec 3, 2007 | 10:48 AM

thirdtimevetteowner

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From: Rochester PA

Thanks for all who replied. I would like to use the FelPro .015" gasket, but don't trust it because it does not have a preflattened fire ring like the GM gasket I mentioned, and the clamping force of alum. heads males me leary also. I want to get to at least 10.5:1, but those damn dished pistons just suck! Why did the gurus at GM put a 58cc chamber with a dished piston? They could have just as easily used a flat top and a 64cc chamber or so. Idiots.
Any more opinions on the .015" FelPro, or any other brand of equal or close thickness, suitable for alum. heads? TIA

Dec 3, 2007 | 10:54 AM

88BlackZ-51

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Quote:

Originally Posted by thirdtimevetteowner

What else are you planning on doing?

Dec 3, 2007 | 11:15 AM

thirdtimevetteowner

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From: Rochester PA

EM muscle headers, true 2&1/2" duals, Flow Masters, no cats, no air pump, Miniram, Comp Cams Pro Mags (1.52 or 1.6, have both), LS7 lifters, tranny upgrade, 2800-3000 stall conv., D44 w/3.54's, and a stout cam. Already have everything but the heads and cam. Oh yeah, an alum., hi-flow water pump and trany/oil cooler, AC delete. Have a DeWitt 2 row rad also. I will be real busy this winter, but will probably do things in stages.

Dec 3, 2007 | 12:05 PM

thirdtimevetteowner

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From: Rochester PA

Thanks to all who replied. If only it had flat tops, the head gasket wouldn't be so crucial. Has anyone run the FelPro .016 with alum. heads? I really want the CR around 10.5:1.

[Fel-Pro Shim, .015 in. Thick, 4.100 in Bore, Iron or Aluminum Heads for use in some sportsman drag racing and flat top piston oval track classes. Can not be used on 400ci engines. Embossed shim with precision coating does not cause any brinneling on aluminum heads. 1 gasket per package!]

Just found these at Scoggins-Dickey. Fel-Pro is a trusted brand name, so I am going with these. #FEL1094 @ $19.95 ea.

Last edited by thirdtimevetteowner; Dec 3, 2007 at 12:32 PM. Reason: New Infomation