Does the engine in question smoke or use oil? The black goo, could be burnt oil from the valve guides leaking out of the exhaust flange. The oil is pumped up the push rods and drains back to the block through holes by the push rods, there is no oil on the intake side of the head. Check the PVC fittings and breather tubes. The valve cover is most likely the source, its pretty hard to get them sealed. Joe
