Hello,
I have had four stock Oldsmobile engines spin bearings. One 403, and three 307's. Everytime this happens it is the 7/8 rod journal that takes the worst damage. Was I reving the engine too much? Is this a coiencedence, or is this typical for Olds engines? None of the engines had more than 100k miles.

Also, is it possible to swap in a 350 crank into a 403, and if so what is involved to make everything work properly/

 

... Which begs the question: How high were you revving them?

Welcome to Classic Olds.

- Eric

 

Longevity depends on maintenance and regular service as well as what has been asked from the engine. It also depends on how well or tolerances when it was first put together. An engine nearing 100 thousand miles in my book is tired. I do not believe the bearings (numbers) that you noted as spinning are a common problem with Olds engines in general.

 

If it is just tired engines, then i'll call it a day and move on. any thoughts on swapping the 350 nodular crank in a 403?

 

Yes, i think this-

If you are going to do that much work, start with a 330 forged crank.

Same re-balance, one more part [flexplate].

FAR nicer piece of metal.

 

The front balancer on the 350n crank is noticibly thicker (and heavier). do i need to rebalance the whole assembly including pistons, rods, crank, balancer, flexplate? Or do I just use the 350 crank assembly and 403 rods/pistons without complete disassembly and machining. I wasn't looking to drop a grand for a crank swap.