[Ross F-1]

Originally Posted by Kube

Within your response is at least one huge clue as to why your engine came apart. You'd told us in the past this particular engine was "rebuilt" twice. You've also been proud (rightly so) to inform us that you've driven a kajillion miles on it.
Now you tell us the crank has never been ground? Um Henry, that engine was NEVER rebuilt. Installing new bearings against an old crank is a certain recipe for disaster. I can only imagine what else was "rebuilt" in such poor fashion......

From Post #110 by Old Henry:

Paul took the whole crankshaft out to check it for wear. It turns out that the bearing surfaces need turning again but if that is done bearings are no longer available to fit it. In other words, the crankshaft is worn out and shouldn't be used any more. That was the bad news.

The good news is that I still have the original crankshaft for that engine that has never been worked and has its original surfaces. Paul was a bit shocked when I brought it in. The surfaces measured 1 thousandth wear is all, plenty of surface to clean up and fit with new bearings for many more miles to come.