Has anyone had an exhaust valve failure. I have a truck that snapped an exhaust valve. The stem is still in the head and retained to the valve spring. The customer had just got the truck back from Ford after a high psi pump change. It lasted 400 miles and lost the valve. The truck is stock except for a 5 inch exhaust.

 

I've seen it once, but it was from someone neglecting to fix blown headgaskets. They kept pushing coolant and they were adding tap water... it leaked into the cylinders so much it corroded the valves into the valve guides and they started sticking... next time he went to start it up, piston smacked valve and broke it off. Destroyed the whole cylinder.

It's really not that common though if that's what you're asking. I can't really see the HPOP being changed effecting a valve either...