Thanks Doug. I wonder, I noticed when pulling the heads that the water jacket slots on at least one pair of cylinders in the center of the block was covered with sealant. I failes to note which slit was covered, but am thinking this lack of water flow could have contributed to lack of heat absorbtion and made it worse. First time I've had an engine with gas ported pistons, also first time I've paid professionals to spec custom pistons and build the engine. Not sure gas ports was the right choice for this endurance project in retrospect, but I agreed to it for the build. Learning as I go...