Jack,
I doubt that even with mis-timed engines you could do that in one hour. Look at the Whyalla engine that was mis-timed, it took a beating for a couple of hundred hours (from memory) and in the end it just accelerated the onset of the crank failure.
Without knowing anything more of the failure it is possible to have cracks between the plug and injector from over tightening and it could be said that where ever the crack was starting was not visible. Perhaps the LAMEs were slack, maybe not. We do not have enough information to comment.
Trent
George is the smartest person I know, and I work with some seriously smart people, and the odd genuine rocket scientist....yes odd as well.