after looking at it further the indention does not go all the way to the valve seat. But it is still pretty deep. Looks like it came from something loose in the cylinder. Im afraid of messing with it because of where it is. This would be a humdinger for a detonation problem.
After removing the defect, use one of those valve lapping tools (a stick with a suction cup on it) and some valve lapping compound to check if the valve makes contact with the seat all the way around. Any auto parts store with have a valve lapping tool and compound.
Apply a thin layer of compound on the valve sealing face and gently spin the valve back and forth for 10 or 20 cycles. Clean off the compound and inspect the valve and seat surfaces. The entire seat and valve surface should have lost it shine and should look kind of dull. The areas that are shinny are not making contact. You can continue to apply compound and spin the valve until the entire surface has lost it's shine.
do you think that this could have put one of the ports out of round? The seats were ground after this occured, obviously, so I wonder if lapping them would show any problems. I'm not really concerned about a flow problem, more about heat and cracks. I guess if I smoothed it enough it would eliminate the chance of a hot spot. The indention being right between the two ports is what bothers me. I'll post a couple more pics
As long as you take the ragged edges off the dent it will be great. No, that small of a mark will not upset the seats. Check the seat, if you must. Either the grinding compound or the ink method will work. I lean toward the ink method of checking. I like sharply defined seats and grinding compound tends to roll the edges .
I agree with Bob regarding compound, I usually use magic marker, but ink serves the same purpose. I looked the pictures and when enlarged they weren't quite as clear. It appears that there have been seats installed,is that the case? If so, that indent may have been put there to make sure the seat didn't come loose. I have seen it done when the machinist thought the seat went in "easier" than it should have. Typically I would have popped it back out and turned down an oversize to a few thousandths larger than that one. If they haven't had seats, it is a moot point. But the crispness around that seat made me wonder. I don't know who did the heads but would venture that the seat was cut after the indent was there so it is probably not a problem, you'll be able to tell more by running some ink,dykem or magic marker on the seat and "lapping" the valve.