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That's still too vague. You'd have a bore with a piston in it. The piston has valve reliefs and you need to know their volume. You need to know how far from the top of the deck the piston reachs when it's at top dead center, and figure out the volume of that area. You need to know the volume of the dish or negative volume of the dome of the piston, unless it's a flat top. You need to know the volume of the combustion chamber of whatever heads you're going to be bolting onto the block. You need to know the compressed thickness of the head gasket you plan to use. (generally, .045" is normal, if I recall) You need to know the displacement of the cylinder, which is bore x 3.14 x stroke.
The result of all these measurements will give you the static (mechanical) compression ratio. Then the camshaft profile and lifter design (hydraulic, solid, roller) will have an effect on the actual running cylinder pressure (also known as dynamic cylinder pressure) at various RPMs. (of course, then volumetric efficiency of the engine will effect cylinder pressure, at various RPMs, too.)
 
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