Crankshaft Bearing Wear and Corundum Abrasive

This is the surface of a worn crankshaft bearing as a result of using corundum abrasive paper to clean the valves in this engine. This is a close-up of the corundum abrasive particle stuck in one end of one of the groves carved by that particle. The corundum also does damage to the cylinders but if finally causes failure in the bearings.