Can some one please give me the low down on compression ratio?

I have a BB 69 camaro with about 10:1 compression ratio. I'm wondering, what is the process of changing the compression ratio to, let's say 8:1 for argument sakes. I guess you have to change out the pistons, I'm not quite sure.

Thanks for the help!

You can either change the pistons, get heads with larger combustion chambers, or put in thicker head gaskets. The head gasket idea is a bad one though as putting in a thicker head gasket causes worse air flow inside the combustion chamber and possibly more pre-ignition. Very bad. The easiest to do then is to put in some bigger valve heads. Can get kind of expensive, but the option of changine pistons could be even more so.

Finally though, there is another way..... sort of. The engine has two compression ratios actually, a static compression ratio and a real one. The static ratio is a measure of the amount in cc's of space in the combustion chamber as opposed to the full swept volume of the cylinder. Thus, if your cylinder has 10 equally sized parts of empty space, at TDC if there is one of those parts in the combustion chamber and 9 below it, you have a 9:1 compression.

The "real" ratio involves how much pressure is built up as a result of the cam. If you have a longer duration cam with a later closing intake, you can bleed off this compression, but still have the same piston/head combo. Conversely, a quicker closing intake can trap more of the air/fuel mixture in the chamber as the piston rises making for a more dense charge and higher compression. Back in the 60s engines advertized having huge compression ratios, but the long cams really reduced the compression at lower rpm because some of the charge could overflow back into the intake manifold as the piston rose in the cylinder and pushed the charge out. Again, not ideal, but it works.