I am getting conflicting numbers on compression ratio from the piston manufacturer and my machine shop.I have a bore of 4.158,stroke 3.76, heads 97 cc closed chamber.I am being told i will get comp.ratio of 9.7-1 is this right.Thanks

You need to know how far down in the bore the piston sits. Head gasket thickness(compressed)? Are the pistons domed (if so, what is the cc of the dome?)? Is the 97cc the actual or was it the starting volume of a stock combustion chamber..if it was 97cc stock, you may need to adjust for any material that has been milled off the heads in the past.

Originally posted by jtm60:
You need to know how far down in the bore the piston sits. Head gasket thickness(compressed)? Are the pistons domed (if so, what is the cc of the dome?)? Is the 97cc the actual or was it the starting volume of a stock combustion chamber..if it was 97cc stock, you may need to adjust for any material that has been milled off the heads in the past. Thanks for the reply here are those numbers.
head gasket .039,domes pistons 182", 97cc stock,piston compression height 1.953 cu, in.

Using your figures above, and ASSuming the following: (you know what that means!) a true 97cc head vol, and head gasket bore of 4.370 (felpro published figure for one of their .039" gaskets), and IF the piston sits .025" down in the bore, and guessing you have a 21cc piston dome (based on speed pro pistons with .182" dome height)...

I used the Pat Kelley calculator and came up with 10.17:1