Well did you want to go 2 or 4 cycle?

I've had REALLY good luck with the SuperTigre 2 cycle engines. I now have the G-51 in three .40 sized planes and have had NO issues with them at all. Easy break-in, easy to adjust, LOTS of power. I have one in my H9 F-22 and it screams with it, as well as a small FW 190D9