[77 TRASHCAN]

Vibrations inside an engine are crazy. More than one would expect.
When Jon Kaase explained his Pontiac Engine Masters build. He talked about crank flex, and that he calculated it into the overall potential of the engine. Nothing I've ever heard, maybe Smokey.......

[PontiacHO]

4 speed car?

[John Milner]

Thanks for the replies everyone. This was in a 4 speed trans am. The cam was a Comp 292. I’m certain the car was driven hard before I bought it.

[Bruce Meyer]

Make sure you mag the crank. I had a similar problem. The outer ring of the balancer slipped. Oil pressure was low. The crank was cracked and was flexing around causing a main cap to crack at the dowel.

[turbo69bird]

Originally Posted by John Milner

Thanks for the replies everyone. This was in a 4 speed trans am. The cam was a Comp 292. I’m certain the car was driven hard before I bought it.

Idk if hard driving would cause that I’ve been running my turbo car w 2 bolt mains for many years running 9s and street driving it really hard as well. Haven’t hurt a main cap. Had plenty of cap walk in turbo engines never a cap failure and I doubt it was running harder then 6
9.70s off the foot brake w a lazy 60ft . Takes a lot of torque through my crank to do that maybe the bad balancer plus the hard driving but even that doesn’t sound likely to me.

[PontiacHO]

Originally Posted by John Milner

Thanks for the replies everyone. This was in a 4 speed trans am. The cam was a Comp 292. I’m certain the car was driven hard before I bought it.

Check for excessive thrust clearance before disassembly. Crank “walking” during high RPM shifts along with a slipped balancer???