Metal spray crank repair?
 

My Gen VI 454 Mag span its bearings 11 hours after a rebuild and one of the rod journals has picked up badly enough that it won't clean up with a grind.

My engine builder has said he can get it metal sprayed and ground to refinish it, would this be an acceptable repair? I am concerned that it would be an inherent weakness.

Personally, I wouldn't do it. I know it can be done, and done successfully. But you have to ask yourself, is it worth it? You can find good used GM steel cranks for 200 bucks or so, or even a replacement scat crank really isn't that expensive in the big scheme of things.

After 11 hours, why did it spin its bearings?

No, I work in a large electrical aparatus repair facility tht utilies metal splaying. We spray shafts that have bearings pressed on them, but not journal bearings. Its not a true bond like welding and it has a tendancy to flake off. You can have it welded and ground, and possibly deal with some locaized hot spots/hard spots, but no spraying. If this is not an all out effort motor, I would just have it welded or replaced based on the cost.

I wouldn't do the spray welding but I would not hesitate to weld and regrind it. Quite a few machine shops have special crank welders. It's not just a regular mig welder. It's actually designed to increase the stroke of a crank. If done properly it can be harder than the original heat treatment. But, you could probably find a good used crank forthe same amount of money.
Eddie

Just having a crank turned cost more then a new these days. Ditch it and start over.

The stock crank is from most likely Kellogg, the nitriding, is very shallow, if it was reground the nitride treatment would be gone and the crank would wear on the loaded side extremely fast. To grind and retreat it's about $435.00 not worth it for that crank. Buy a new 1 piece, externally balanced crank from either Callies or Scat. A new one from GM is about $1200.

Thanks for the advice, I am based in the UK so finding a good used forged crank is not so easy, hence the need to repair it. I'll reject the metal spray option and instead see if we can locate a good place to get it welded and reground.

My main concern is to discover why it spun the bearings after only 11 hours, at the moment it appears to be oil starvation but I need to pin down the root cause.