As Nathan says, they are torquey motors, so the gearing must be changed, though you could also use a higher voltage Lipo (I know some people who are using about 1100kV motors with 22.2V) to counter this too.
It is a lot easier to go with the car motors though, although Neu's, Hackers, Lehners etc are all originally Heli/Plane motors anyway. Even the Castle Neu's are based on the original Neu motors, so are really heli/plane motors.
__________________
|