These distributors come with an O ring for the distributor to engine block interface. I'm not talking about a leak there I'm talking about it in the upper electrical area, and supposed measures where done for that just in case scenario, just not done properly on these units. Some how the oil must capillary up the shaft on some units and cause it, maybe the shaft finish etc etc. like auger effect. Maybe PCV is a help, PCV was used in 1957 on some big truck applications I think it was.
There is no provision for any kind of seal at the top bushing, there is a deflector cup though.
