My brother just bought a used 426. I checked the oil pump. Looks like metal pieces went through rotors, according to marks on rotors and sides. How critical are these marks? Must I replace the rotors or cover plate/housing aswell? Can I test the pressure of the oil pump somehow? The oil side water pump seal had blisters on the side where the numbers are. Could this be from overheating? Valve clearances I shimmed. Clutch basket I filed notches out. What else must I check? How can I check timing chain and piston without tearing apart?