I've read that a cam seizing up can be one cause of sudden timing belt failure. What can cause this to happen, and how might you tell with a dead-in-the-water engine that a stiff or seized cam led to the death of the belt? Should the cam turn easily and smoothly when the belt is gone? Can the cam bearings get so nasty with the residue of dirty oil that this can happen because of it? If so, can polishing or cleaning the bearings make the cam turn smoothly again and revive the engine?

Thanks very much in advance!