We also discovered on the dyno back in the early 80's that the distributor also is the source of a pretty large internal oil leak on virtually all engines that have the distributor as part of the oil route. We created what we called "left side oiling", which took the distributor bore out of the oil route and diverted it down the left lifter bank and crossed it over at the front cam bearing to feed the right side lifter bank(V8 of course). This mod yielded a steady 10 psi increase in idle oil pressure with wet sump systems, if that gives you an idea of how bad a leak it creates. The distributor fits pretty sloppy into the bore in the block and doesn't seal around the oil galley path well at all, especially depending on the machining tolerances of both the block and distributor housing. It can also lead to oil pressure problems that are hard to pinpoint even in fresh rebuilds.
