I'm almost there!!!!!!

[one2dmax]

I think there are way to many variable factors to accurately use math with the data we have available. The engines running condition, valve adjustment, exhaust configuration, timing, compression, intake restriction, filter restriction, intake velocity, exhaust overlap and velocity, float level settings (a big factor), vent hose configuration and more. Basic math can tell you the approx amount of CFM a pump can cosume at a given volume and RPM.

Here's one with the math already ready for you.
http://www.widman.biz/English/Calculators/CFM.html