I built an engine for my car last year. It included having the heads worked over with CNC porting and new valves and bronze guides. Car ran great until an intake valve seized in the guide and stuck open. Started tearing things back apart to see what happened. Turned out the valve guide was chewing itself up so bad that all the metal chips jammed between the guide and stem, sticking the valve open. I took the rest of the the head apart and almost every guide looked like the pictures. All those bronze chips were sitting behind the valve seal, and the valves were pretty loose. I was obviously confused and disappointed by the whole thing; I had maybe 250 miles on this stuff since it was assembled. I contacted the head builder and he said he's never seen that before and has no idea what can cause that. However, he took care of me and redid the heads. I've got a few hundred miles on them again and everything's fine so far, but more time will tell if everything's good this time. So my question is has anyone seen something like this, and does anyone have some knowledge as to why this would happen? I'm super curious to know, even if I don't have anymore problems.