Good things gone bad

I knew the intake valve was wasted. It was so rusted that when I brushed the rust off, it had deep rotted pits. But I cut a fresh valve seat and face and ran it. At the last race of the season last year it held up. However on the first lap of the first race of this season it let go. This is how I do R&D. My dumb ass ruined a nice old Bruce Sass ported head. Damn it!