Hi All,

I know it's not an exact science but I was wondering if there was a formula that gets you in the ballpark? I figure with a known cylinder volume and a compression reading one should be able to get in the ballpark with a compression test reading.

I have heard that an 18:1 engine has a compression test reading of about 350 psi. No matter how I slice it I can't seem to come up with a formula that comes close to 18:1. Again, I know it's not an exact science as you really need to take into consideration head gasket thickness, head volume, etc but a simple compression test should be able to get you close I think? Any one know of a ball bark formula?

Art.