I had one twist off on the engine after running it to warm the oil up on the dyno after 10 to 15 minutes, this was a new World iron block that had not been machined correctly on the oil pump mount pad, it had a tiny ring (.0003 to .0009 or so) that was sticking out around the oil pump drive hole but not enough to see or feel until using a straight edge across it trying to find out why it broke that shaft off while dyno testing that motor in Boise ,ID for a customer who lived and race there.
I had called my wife to have her bring me the last new one I had in stock back home in Bend and had her drive to Burns, OR (about halfway between Boise, ID and Bend)
The dyno operator found that ridge and had removed it by the time I got back and took it in to the shop the next morning
I hate Murphy