I am a huge fan of Irvine airplane engines. Haven't tried the irvine heli but i hear they make a quality 39 heli motor that is worth a look.

I tried the OS 50 Raptor a couple weeks ago. Very sweet. lots of power, easy to tune. very littel fussing to get the power you need without overheating. The down side is it drinks fuel like crazy.


charlie is right about head speed, these engines are happy running a littel faster that the 1500-1600 everyone recomends. might be a good idea to upgrade to carbon or glass blades to take the extra RPM, added benefit, they are more efficient than the woodies.