well I would like to know if I could use a car enigne (nitro) with a small prop???
if it is possible what prop will I be needing then???
another option is gearing the engine down (I don't know how much rpm the most "speed" engine have... and I also don't know how I could achieve that)

Jacar

I trust you are speaking about modifying a 2.5cc (.15) car engine for r/c combat use? Assuming the crankshaft is long enough, and there is a drive washer on it (or you are able to make one if there is not), it may very well work. I have not knowledge on how car engines are timed compared to airplane engines, so my prop reccomendations may be off, but I would suggest an Master Airscrew 8 X 3 "Combat" prop, or the likely more available MAS or APC 8 X 4 prop. You will want rpm in the 17K to 18.5K range. Hope this is a starting place for you....
GPB

well, its a 2,1cc car engine (nova mega .12 wich must be able te get around 35k...)
I think the crank is long enough but it has no washer but I can make one my self.
but I don't know the timing thing...
could you tell something about that?
because I don't know much about the diffrence of the engines... (I just fly a bit and a friend had this engine for a nice price so I bought it...)

Jacar

I am afraid I can't help you regarding timing. Maybe someone will step in and have a good explaination about the difference between a car and airplane engine's timing. If it's a .12, I would stick with the Master Airscrew 8 X 3, or maybe even a 7 X 3. Good luck!
GPB