I wouldn't think that a four stroke would make a good car engine because you couldn't mount on of the big heatsink heads on it. Cooling would be a real issue I would think unless you had some sort of fan arangement to keep a steady flow of air across it.

Power wise and realibility wise, they are great. They won't crank the high RPMs that the 2 strokes do, so again that may prevent it from being what you want. 10,000 it a rough rule of thumb on them. Just like a real car four stoke, if you run to fast, the valves well float and then who knows what might happen. I have a 70 Magnum that will run up to 11,000 but I detune it to top off at 10,000. My smaller 52's are good for 9800 to 10,500 depending on the props used. The four stroks have good low end torque so acceleration is good with them.

Don't know if this answered your questions, and I'm sure someone out there has a better prespective than I do on using them in a car.

Don