I seriously doubt that, based on the OP's original post, that the valves hitting the pistons are the ONLY problem. Normally if you have P-V clearance issues, it will show itself within the first seconds of initial fire-up, and if it doesn't show then, it will show itself on the first burnout. Been there, done that. And even then, worst case scenario, valve heads would break off and you'd see all kinds of carnage, jammed into the heads, piston tops, etc. Normally, just lots of bent valves (all of 'em).
He said that it slowed significantly before it broke, like it was "locking". Usually that means a bearing spun or stacked, and if it's not caught and shut down quickly it can lead to broken cranks, rods, etc.
Now I don't know what kind of timing chain set is in that engine, but I've seen many a double roller chain BREAK when something lets go. Sometimes even something as "simple" as a rod breaking...can cause the crank to get jerked around pretty hard and bust the chain. If the chain breaks, inertia of the crank, converter, the car rolling forward and spinning everything....well if the cam stops and the pistons are moving, you'll have bent valves usually.
I have been through this stuff many times unfortunately. 99% of the time when I had bottom end failures of some sort, the valves get bent or broken. I like to use undercut stemmed valves because they will bend most of the time rather than break. At least that way I can salvage some pistons for maybe a future build. And possibly save the head(s) as well.
But from what I've read in this thread, lots of folks are saying that the valves have hit the pistons and caused the holes in the pan. I say that is just not very likely. Like I said, usually if the valve were hitting, they'll bend or break...usually bend....but that doesn't explain why there's dents in the oil pan
Either way we look at it, it is still very unfortunate.
