Quote:
Originally Posted by Rocky Rotella
If you plan on reusing the crankshaft in the engine, I strongly suggest having it mag tested to make sure it's crack-free. Generally speaking, if a balancer isn't torqued properly (particularly to the point it breaks), it can't dampen harmonics correctly, which forces the crankshaft to dampen them. That can then lead to fatigue/cracks in the cheek area where the journals meet the counterweights over time.
I also see the "77" on your block. It it happens to be a 500557 casting, they have the thinner main saddles, which may have also been affected by having to absorb the harmonics. I'd suggest having it mag tested too for piece of mind.
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Very true, the 6.5 diesels have a habit of slipping the rubber on the harmonic balancers when they get older. If you don't catch the problem as soon as it happens, the crank will break. When the ring slips it makes noise from the ring hitting the pulleys, and timing cover.
There are a ton of 6.5s that break cranks due to this problem, so many in fact, that the after market now offers a forged crank for these engines.
As has been mentioned also, the block main webs also break in them due to the slipped balancer problems. There are blocks that GM cast for these engines that are weak like our 557 block is. Casting numbers to avoid, if you ever rebuild one of these engines.
As recommended, check the crank and block for cracks as long as you're pulling the engine down anyway. It may save you grief down the road.