the outter cam holder (hopefully we are talking about the same part here) that the distributor bolts up to needs to have some liquid gasket applied to it before it is bolted to the head....think about sealing the entire engine....you have the head gasket between the head and block, and the rubber gasket between the head and the valve cover....the only area not gasketed is where the cams enter and exit the head....sure the cams themselves have rubber O rings on them but what about where the outer cam holders are exposed....this is why liquid gasket needs to be applied under the outer cam holders!
that is a pic from a helms for a B18