Knock and smoke

It kinda looks like that piston was hitting the valve. Did you check for piston to valve clearance when you assembled the engine? Maybe the 508 cam was too big for the notches in the pistons.

Hate it.

Another theory is that the valve was hitting the piston from the get-go and was getting bent so the thing would not return fully to the seat. The lifter started to pump up and the cam kept trying to give the valve full lift but starting from a point of already having some "lift" due to the valve not being all the way down in the seat. Eventually the lifter pumped up enough to cause the thing to hit hard enough to fail the piston. There are clearly witness marks on both the valve and piston from contact.

If the cyl hydrauliced it would not have caused the valve to get bent.

My stroker has a cyl sleeve in one of the holes. Can a cyl be sleeved even after a piston knocks a hole in it?

I didn't like the paint on the valve train either. Somebody has been doing some serious corner cutting. Cost a motor.

Still hate it.