What causes this to happen? On a fullt built motor, I dont assume this should happen. But it did, just wanna find out if its an clearence issue or motor not balanced correctly when being built or what??? Any inputs!

 

Unbalanced bottom end, lack of oil, heat, clearances too tight.. I can also see a case where a screwed up oil pump gear can throw the balance off and do this.. What bearing did you have that spun? Was it a main or a rod bearing?

 

Rod bearing on #2, b18c block with eagle rods

 

What was the clearance of the bearing?

 

Motor was built by someone else, never checked it!! Should of but why.....made awesome numbers.. but the spun bearing is just something that I want to know what causes it. I'm pretty sure it was in spec, was dynoed for a period of time.

 

When I spun a bearing it was due to a rod bolt stretching.

 

On a properly built engine, if you spun a bearing chances are its due to oil starvation.

 

Thanks for all the inputs. What can you do but keep building them.