ive not seen a running engine that bad before, looks like its been stood for years,and the water( without antifreeze ) has gone from the waterway to the fire ring,and corroded the head,what was the gasket like?
pics can be deciving,but that doesnt look like it will skim out.
can you get det under the fire ring?i would have expected a lot more damage around gap between the valve if it was caused by det.
is it just the one cylinder that has the problem?