[Jeff Alton]

There is no gasket between the heads and the cam housing, just some loctite sealer. Simon was not refering to the actual valve cover. He was refering to the rocker shaft itself. They can and do leak where they seal into the cam housing. It is a shaft that has a pressure fit. When the bolt that goes through this shaft is tightened upon installation, it expands the ends of the shaft to seal it the camshaft housing. This is a fairly common leak and there are now rubber seals to help solve this problem. If this is where your engine is leaking, It can be repaired with the motor in the car.

Cheers, Jeff