I have intentionally posted after typing awhile because in the past this server will time out and I am not retyping all this again if it gets timed out so bear with me here.
It seems GM pretty much used the same type bushing in all the iron case distributors. I’m going on a limb and gonna say something like a 660 oilite type bare bronze bushing. You can usually tell if a bushing is porous by placing it in a hot plate and watching the oil wick out onto the plate. I’ve got a couple of GM prints on these somewhere in a folder that stipulates exactly what they were.
They pretty much ran this deal until the switchover to the aluminum housings, where they kept the same deal for several years after. Somewhere up in the 1976-77 year range, we started seeing a new top bushing appear that had a chrome plated outer jacket. These are carried all the rest of the way through production until Delco ceased manufacturing of the GM housings that we know.
Early on the distributors upper bushings had a single 1/16” hole in them in line with the bottom 1/3 of the grease well. It is worthy of note to explain that the cast iron housings had more of a round trough cast in the upper housing. Therefore one single hole did fine as the hole was supplied access by the whole trough.
The later aluminum housings went to a lighter weight design with 5 distinct cavities, all fairly well sharing access to each other. These designs utilized the commonly seen bushings with 2 individual 1/16” holes opposed from each other.
Over the years the grease changed composition roughly 3 times and very early on the grease was actually a sawdust pickled in heavy weight gear oil. The grease never was of the high temp type for reasons explained later in this text.
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