Took the heads back to the shop and they took the offending valve out. It wasn't a tight guide. Somehow something melted to the valve shank when it was open and it jammed into the guide. You could drop the valve in the guide upside down and it was free until it hit the bad spot on the valve. No idea what it was.

He offered to get another valve and install it but I just had him file down the spot since it was only about 1/4" from the end of the guide when closed, polish it, resurface the valve, ream the guide and reinstall.

Since I was in the neighborhood, I dropped them off at my machinist to machine the valve cover sealing surface. It was pretty rough and I can't get them to seal. Should fix that problem. Should be done next week.