/wwwthreads_images/icons/wink.gif I think what you do is take the displacement and multiply by the volumetric efficiency, and that is the volume of air for two turns of the crank. Divide that by 2 for one turn of the crank, then divide by 1728 to get cubic feet for one turn of the crank. Then it is turns per minute (RPM) times cubic feet displaced per turn. Turns cancel out giving you cubic feet per minute. So, let's try that on a 258: 258 X .78 (Just a guess at what the volumetric efficiency MIGHT be) = 201.24 divide by 2 that gives us 100.6 divide by 1728 that gives us .06 (cubic feet of air per revolution).....multiply that by four grand (4000 RPM) and we come up with 232 Cubic Feet Per Min (CFM) Not much is it. so you can see that unless you are twisting it to never-never land on the tach, that a fairly small carburetor will suffice./wwwthreads_images/icons/crazy.gif
I never believe any statistics unless my moonguys /wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/wink.gif made 'em up themselves.