RE: go fast engine for a 1.40 size airframe?
Don't know the airframe yet (an that will change a lot)
But a ball park engine could be a moki 180, based on the 150 moki it'll pack a punch for it's size, it ain't high revvving, but there isn't much going of that size that is, i'd say a tuned pipe and coarse props would give you plenty of punch... supertiger make some big cheap two strokers too ... think theyre on the heavy side but run reall good! at the top end there is the OS160fx which is an expensive motor but would rev well for it's size on a good pipe too!
just some suggestions .. knowing the airframe would be good tho .....
just my chip
Henley