Posted for "Bruce Gray" <Bruce@glasair.org>:

 Your engine is an air pump.
 
 Displacement times RPM = Cubic inches per minute divided by 1,728 (Cubic
 inches in a cubic foot) = cubic feet per minute of air needed (add a fudge
 factor of say 20 percent to allow for filter blockage by dirt or ice.)
 
 Bruce
 www.glasair.org