This was my first though when I saw your first post. The left side is just too clean. Before going any further with taking things apart, do a coolant pressure test with the valve covers off. This should show where the water is getting in.There has been a coolant leak with this motor. Engine oil analysis report says coolant in motor oil.
If it were a small crack, you would see the cleaned portion just beside the crack. Mine was a very slow leak, and the area cleaned was small, just around the bolt head:
Latest oil change/ oil filters
I just pulled the valve covers to inspect the head. It is not a Castech, BUT it is cracked in the same position that the Castech heads were cracking. Time for new heads. In the oil drainback hole you can see the crack before I pressurized the cooling system. I already cleaned the area for...
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Was there any other unusual wear according to the report? I suspect the coolant leak is/was quite big, and may have caused other internal damage.