Was dead on positive thinking we had spun a rod bearing pretty bad. Pulled the motor, got it on the stand, pulled the pan, pulled all caps off. Didn't see any spun rod or main bearings, only one main bearing was slightly scored. There were metal shavings in the pan though. This engine was knocking loud as a mother****er too, it definetly sounded like a rod knock. I checked the tranny bolts, and the flywheel isn't cracked either, and the bolts were damn tight. Me and my neighbor are stumped.

Edit- the motor was rebuilt 500 miles ago by the previous owner, and its bored 30 over

 

did the noise quit when it warmed up i.e. hellashish piston slap?

 

pull heads look for lost bolt?

Check wrist pins.

Front damper keyway. I had one that sounded like a rod, but the damper keyway was badly worn. crank was okay. new damper and key all was well.

I know plasti gauge is not recommended on this board, but it might lead you to something that is way out of whack.