Quote:

I would want to know where the metal came from while still under warranty.



Normally just a bit of swarf from improper cleaning after machining. Or a little chip from the casting that came off under load. Probably came from inside the head (casting) and during one of its shutdown cycles it blew out and got stuck in the valve. Was it a brand name or the Harbour freight cheap China stuff?. Chinese Castings are still fairly poor especially on the lower cost items.

Change the oil, tighten the head bolts (not overtight) after a few hours of operation, and drain the receiver (air tank) every now and then using the petcock at the base of the tank and it should last for a long time.

Adventure before Dementia...