So I bought this mini at salvage auction. It had mechanical problems. I was hoping it was a timing issue, but timing was good. One rocker arm was sitting under the intake cam. So what would cause the rod and piston to blow apart? The head appears fine. I haven’t dug in to the engine other then removing the head. I’m in the process in removing it.

 

Not good. Ring failure maybe or piston failure. But hard to tell, maybe it was ran low on oil? Hard to tell without the history.

Sorry to see this.

 

I wish I had the history on it. The crank journal for the piston actually isn't that bad, but will need to pull the pan to satisfy my curiosity.

 

It looks to me like the piston failed and then the wrist pin came out and the rod went through the block. that's not generally from oil starvation so you'll likely see reasonably clean crank journals and a bent rod (and mabe an bent crank)

why did the piston fail? lots of possible causes. Heat (lean burning), mechanical failure, hydrolock, defect, etc. but until you get it completely apart you're not going to know.