47-59 If it weren’t for bad luck

[1project2many]

That there is a no fun situation. The top picture is definitely piston chunks along with the circlip pin retainer. I'm not sure I recognize the pieces in the bottom picture. Do any of those pieces besides the wire retainer stick to a magnet?

Damage like this can be caused by insufficient ring end gap. It looks like the pistons have dry film lubricant coating. They're likely not cheapies. Did the noise start just after a blast on the throttle or just after a coastdown?

[autowrench]

Dang, that's tough! Definitely a piston hand grenaded. I don't remember, was your engine a gen 3 or 4 Vortec? The AFM caused some real problems for some folks. I know you are not the original purchaser, but maybe you could reach out to the builder and see what they might do for you?
Tom