formula one air racing is still expensive.
yeah it uses the o-200 continental....but they spin them at 4000+ rpm's...direct drive to the 4-foot diameter prop. You need a valve job every 15 to 30 minutes at race revs, and itll eat up parts that arent designed to do this RPM..... youll need alot of cylinders, springs, valves, pistons, cams, gears to do it with. and a crew to help.
theres the F1, biplane, T6, sport, unlims.....the F1 seems the bargian....but its still costly...
There is the handicapped cross-country racing...point to point stuff. thats pretty popular. places like Sun n fun run stuff like that...the sun 60 i think they call it.