Here's the broken crankshaft. I converted the engine myself. I had 120 hours on it when it failed. The failure may have been due to an out of balance propeller.

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Comment by Dan Dempsey on August 16, 2021 at 6:44pm

It could be that Mark.  I checked the radius when building the engine.  All were well within spec, but then again that was the GM spec, which I suspect isn't adequate. 

Comment by Mark Wood on August 16, 2021 at 11:17am

I think the reason for the who question is that the crack originated in the rod journal and propagated from there. This often occurs as the result of inadequate radius in the fillet. A sharp edge in that portion of the crank will cause a crack which, from the striations in the failure, look to be the case. 

Comment by Dan Dempsey on August 9, 2021 at 5:15pm

Peter, I had the crank ground by a local speed shop.  It was then nitrided by Pramrod.

Comment by Peter Eiberger on August 8, 2021 at 10:55pm

Who ground/nitrided the crank?

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