I'd have to trace an oil circuit to be sure, but I'm going to make a SWAG that the oil distributor became non-functional once the oil supply moved to the rear cam bearing oil gallery. A simple 1/16" orfice would have been all that was necessary to restrict oil flow to the rocker arms in that case, while still supplying sufficient oil to lube the rockers and valve stems, similar to the flow control used for a bypass oil filter. I have seen many stovebolt rocker arm systems that have obviously been running virtually dry for thousands of miles, usually with the bottoms of the rocker shafts seriously worn, and the rocker arm tips deeply pitted from rubbing on the valve stems with no lubrication. For some reason, there has been little or no wear to the rocker arm bores in those situations.
Jerry
