Is it okay to run a .12-.15 size car engine in a .10-.15 size plane? I've noticed that some of the new ones have RPM ratings up to 43,000 or so, HP ratings (for .12's) of 1.5 hp @ 38,000. Considering pretty much all car engines are made to run with a tuned pipe, I wouldn't mind putting an engine like that in a small plane.... HOT DOG!

Why don't I see more car engines in these smaller airplanes?