How do you figure out compression ratio before build?

Just curious, how is the compression ration calculator. Long story short, I'm going to be building my 400 small block to put a blower on it and I don't want to go over 9:1. So between, pistons, rod length, crank, heads, etc, how is it overall figured out accurately. Thanks

Well first of all, if your pistons are made for your rods then rod length has nothing to do with it:)

But it's pretty simple, you need to know your bore, stroke, piston volume, combustion chamber volume, gasket thickness, and how far "in the hole" your pistons sit.

Basically the calculator takes those variables and figures out how much volume is in the cylinder at bottom dead center, then how much volume at top dead center. And that give you your compression ratio.

Hope that helps,

Jeremy