Compression Ratio

[spitzerscott]

If a set of pistons is advertised at 12.5cr with 64cc chambers, and I have 58cc chambers what would I end up with for cr? I know there is a formula but I'm trying to do it the lazy way.   Thanks

[noslin]

http://www.gtsparkplugs.com/CompRatioCalc.html

try that maybe. 

[msundstrom]

The FIE web site also, Spud has a very user friendly Compression calculator. Think it bumps it a little over 1 point @ 58cc.
Mark

[spitzerscott]

The reason why I am asking is, without taking the engine apart I cannot fill in all the blanks. But I was told to add about 1 point. Just thought someone could confirm.   Thanks

[wideopen231]

actual bore and stroke number will change outcome of clculatios. A bigger engines number will be totally different  than smallier engine. Larger engine  easier to build compression in.

[spitzerscott]

This is a 336 SBC

[Frontenginedragsters]

This is the calculator I use:
http://users.erols.com/srweiss/calccr.htm

[Roger]

336 small bocks are usually a 0.060” over 4” bore with a 3.25” stroke. With a piston dome of 13cc, a chamber volume of 64cc, along with a 0” deck height and a 0.041” thick gasket with a 4.1” diameter, that come out to 12.5-1cr. Put a 58cc chamber on that combination and that comes out to 13.8-1cr. Or something close to that.

[spitzerscott]

Thanks Roger, that's what I was looking for.