I did this conversion and didn't believe the RPM numbers so got a buddy's tack to verify the numbers. The prop was an old Dynathrust 20-10 that I had in a drawer and had never used. Only good for stiring paint. I would like to see what this engine will do with a good 15mm WT carb and an APC prop. With this kind of performance I will buy one of these engines for a 1/3 scale Cub I'm planning.