i cant offer any info on the o.s. line of engines, but i have the evolution trainer powerplant on my debonair. it screams. it was $80.00 at the store. it is easy to tune and is already broke in from the factory. it is .46 in size and has bearings. very good engine for beginners to start and grow with. everyone at my club likes it alot. and it makes that deb go, go, go. i just put a 2 blade prop on mine(broke my 3 doing high speed taxiing in 30 mph wind on pavement. lol). 2 blade is cheaper and easy to find.