Well there are bearings, but they are solid steel, and really thin. They sit in the main bearing caps, and are smoothed considerably. They get oil from little holes in the middle, that then runs down channels in them. I'm sure if you were to break down a lycoming, or continental, they would use the same style bearings to support the crank shaft, and connecting rods. Also, the camshaft probably run on them too. This is what main bearings are.

For a radio, I would reccommend airtronics. Not too many people like to talk about them. I don't know why, since they are just as good as the others, and so much cheaper than Futaba, and especially JR.