Originally Posted by 95chevy406
Raps light when idleing and goes away when rpm goes up.tore motor apart and have gouges in main bearings and some are chrome looking and others look like bronze or had a bronze coat that looks to be wearing off.also had no oil pressure after motor was warm.motor is a 72 400 bored 406 that had new pistons and bearings when i got ut.
Does it have arp rod bots? Were the rods resized or are the big ends round now. Sounds like it used up the bearings bronze is the base metal the bearing material is grey like zinc colored.
High rpm engine? It may have just had cheap bearings with a little too much clearence. High rpm engine can beat them up pretty quick if the clearence is off either way.