I think that we can have great confidence that things don't happen for no reason. But I cannot reasonably see how the balancer spinning on the crankshaft could cause the pulley bolts to shear. Loss of torque or fatigue would seem to be a more likely cause.

You are obviously thinking about a different engine than a 617. There is absolutely no woodruff key associated with the balancer on a 617.

I would imagine a startup on either the seized alt. or A/c comp would be a reasonable suspicion. They are definitely intended to shear before doing harm to the rest of the crank

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It often doesn't happen that way. Sometimes, dowel pins shear and the pulley bolts survive.

I guess I was thinking about about those two pins on the balancer as the woodruff key. My bad OB1.

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1983 123.133 California
- GreaseCar Veg System

I suspect that we would have been much better off if MB had used a Woodruff key instead of the dowel pins. It certainly would have allowed for easier balancer installation, as well as improved reliability. Maybe there was a reason Mr. Woodruff received a medal for his invention!!! (As far as I know, Mr. Dowel received no such recognition!!! Rightfully so, apparently.)