Wallaceracing.com has awesome calcs that will tell you pretty accurately what your flow numbers are based off cfm, ci, bore, stroke etc.... You need quite a bit of info to get really accurate but it does work and can you tell you a lot. Volumetric efficiency is what you're after I think. Get some base measurements and figures of your engine and plug and play with carb cfm and manifold cfm based on what's available for your project.
