Hey guys.
I am trying to figure out my CR. For simplicity's sake, I am comparing my rebuilt 357 shortblock to a new GM shortblock. They both have -13cc 4V relief pisons, stock deck height, and 58 cc heads.
The GM one gets 9.5:1 CR with the stock 4" standard bore pistons and .039" compressed thickness head gasket.
My shortblock has 4.040" pistons and i am thinking of going with a thinner .015 head gasket.
Is there a way I can figure my CR from this info?
Thanx in advance


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'88 RS (originally 2.8)
-350, .040 over, vette alum. L98s, stock tpi.
-305 injectors & chip
-TES headers & edelbrock cat back
-3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
on a 2.050 60 ft.
(Damn the 2.8!)

 

What you can do, is use any of the compression ratio calculators on the web, use a number like .1 for deck heigth on both, then compare the different ration with the different gasket thickness's, then add the difference from the GM crate engine.

i/e using .1 for deck heighth may yeild 10:1 on the crate engine, and 10.3 on yours...so add the .3 from the GM 9.5 and it should put you right there.

Ofcourse if you know the deck heighth, you can nail it right the first time.
><><>><

Typo king at work



[This message has been edited by 8Mike9 (edited November 23, 2001).]