Hello all. Have a 350 one piece that has spun 2 and 4 main bearings. Others look ok. The rear main bearing has the thrust surface worn down, and the crank was somehow thrust forward. Any ideas? there were lots of copper chips from the bearing thrust surface being chewed away. That may have caused the bearings to fail, but why just 2 and 4?

Engine is in a boat with an OMC Cobra drive, maybe the gimbal bearing failed and thrust against the crank.

Anyway, just wondering why only 2 and 4 went south real bad, but the rest are ok, even the rear main on the journal portion.

Thanks

 

The metal shavings got pumped to them 2 cylinders the the oil pump has to pump the same amount of oil to each cylinder and the oil supply going to them 2 had shavings in the oil
there for causing them damage the motor may have been starving for oil

 

Depending on how hot they got, the block may be garbage. The caps could be distorted and will need to be replaced. No matter what, the block will have to be line honed. If the main bearing webbing got too hot, it may not be repairable.