I'm trying to further my education in the world of engine building and need guidance from wise sages. From what I think I know, an engine is an air pump. Bore and stroke dictate the displacement which is a fixed or constant volume of air (cu.ft.). When you bring rpms to the mix, volume over time, cu.ft. per min. or cfm. As rpms increase so does the cfms of air needed. A formula I found that is supposed to give a starting reference goes as (cu.in x rpm)/3456 = peak cfm for peak power rpm. Granted this is a base or reference figure and im sure dyno results will prove more reliable. My question is this, I have seen some of the drag bike videos, the mini bikes with some wicked gx200 with 3" bores and monster strokes guessing 3" +/- . So 3" bore and 3" stroke would give you 21.21 cu.in. I'll call 22 cu.in. and I've seen cfm claims of over 100 cfm on the flowbench. But using the equation above shows 66 cfm to support 10,500 rpm, 89 to support 14,000. So am I missing something or what. I mean I know an engine will run no matter the size port but was always told to get the port big enough to just flow the needed cfms so port velocity stays high to aid in cylinder filling. An engine can only take in so much air per intake stroke based on the displacement so seems like going bigger wouldn't do much good. But then again my formula may be way off. Also these bikes are built for top end power in straight line acceleration drag racing, much different than what goes on a dirt oval. Also I know airflow has a direct correlation with hp, the more air fuel in, the more power out. But with that said, I don't think if you port a head to support 60 hp and put it on a 200cc engine, that engine will put out 60 hp so there has to be a point at where the port just gets too big. Anyway if someone could straighten me out on this i would appreciate it. Not trying to ruffle feathers or call anyone out, just trying to learn. Thanks