I think the same areas where you are seeing the piston scuffing coincide with places where the head gasket is very close to the intake valve. This is probably detonation, maybe even pre-ignition.
Have you ever laid a head gasket on the head and noticed the relationship between the fire ring and valves is not the same for each cylinder? This is with the stock head gasket or the one that comes in the Fel-Pro HS 9441 PT kit (perhaps there is another gasket that does not have this problem?). On the driver's side, cylinders 1 and 3, the head gasket is very close to the intake valve. Not good for preventing detonation/pre-ignition. On cylinder 5 there is a fair amount of distance between the intake valve and head gasket. On the passenger side cylinders 4 and 6 have the head gasket very close to the intake valves. On cylinder 2, there is a fair amount of distance from the intake valve to the head gasket. I am betting the detonation / pre-ignition cycle comes on cylinders 1, 3, 4, and 6 because there is a hotter heat source that may not exist for cylinders 2 and 5.
Have you ever laid a head gasket on the head and noticed the relationship between the fire ring and valves is not the same for each cylinder? This is with the stock head gasket or the one that comes in the Fel-Pro HS 9441 PT kit (perhaps there is another gasket that does not have this problem?). On the driver's side, cylinders 1 and 3, the head gasket is very close to the intake valve. Not good for preventing detonation/pre-ignition. On cylinder 5 there is a fair amount of distance between the intake valve and head gasket. On the passenger side cylinders 4 and 6 have the head gasket very close to the intake valves. On cylinder 2, there is a fair amount of distance from the intake valve to the head gasket. I am betting the detonation / pre-ignition cycle comes on cylinders 1, 3, 4, and 6 because there is a hotter heat source that may not exist for cylinders 2 and 5.
