Just to put this out there....not a reflection on the Promaxx stuff. But I would find someone that has real world experience with them from a durability standpoint. My buddy just dropped off his truck with a very nice 496 stroker BBC short block topped with offshore heads and the quality of the guides and valves wrecked the whole thing. I am talking about mushroomed valve stems to the keepers , a valve that dropped a head off with no prior evidence of touching anything, valve to piston was .270, and valve guides that are .030, yes .030, out of round.

The heads were very nice out of the box...I could not tell the metallurgical make up of the parts though.

the casting looks ok even after all the destruction...... no

Has anyone run these heads for any extended period of time?