Ed, looking back at your previous post, you seem to be under the impression that increasing the bore (swept area) is related to the compression ratio.
It's the piston design that changes the compression. It essentially decreases the volume of the combustion chamber (at TDC) in relation to the total volume of the cylinder.
That's how, back in the day, you would have the same engines in cars with different compression ratios. e.g., 327ci base two bbl carb, 8.5:1 compression vs. 327ci Corvette engine 11:1 compression. Different pistons (among other things). But the pistons are what determines the compression ratio.
