When you see oil INSIDE the distributor (under the cap) particularly near the rotor shaft (under the reluctor ring) it probably is not related to the O-ring which is located on the outside of the distributor housing where it inserts into the head.
The leak could come from a couple of sources IME; first is a bad rotor shaft seal which is located beneath the reluctor ring (the thingy with the teeth on the shaft). That seal is essentially not replaceable, at least not easily because the pinion gear on the engine side of the distributor is pressed on to the rotor shaft. Most other distributors have that gear pinned on and it can be removed easily, not so for our distributors.
One other possible cause of the leak, if the source does not seem to start from below the reluctor ring, is if you have a large oil leak from the O-ring or the valve cover, and you have a lot of oil blowing around the distributor it might get past the distributor cap "packing" (rubber gasket) or maybe if there is a very large leak it might get blown into the breather hole located on the top backside of the distributor housing. The oil pattern under the cap should give you some clues as to the source.
But again, if you see oil around the shaft at the bottom of the housing (internally) where the shaft dives into the distributor housing, as in the photos above, it is a bad shaft seal which is essentially not replaceable. If you do take the distributor apart (press off the pinion gear) that seal is not available as a separate part from anyone.
You would have to find a replacement rotary shaft seal, and no one makes that exact same size or design. The closest I found is a slightly shorter seal that should work, but may not last as long as the original as the sludge and grit from the old cooked oil that gets trapped inside the housing can get right up to the lips of that seal. The OEM distributor seal is better protected due to a unique shielded triple lip design.
There is also a shaft bearing that receives it's lube via oiling slits located in the narrow part of the housing that sits inside the head. So if you have oil getting past the seal you also have oil getting past the (single) seal on the bearing. This bearing is also a unique design, but a standard size, so there are substitutes that will work.
So what to do? First, do NOT use carb cleaner when cleaning off the old oil from inside the distributor, that can damage the seal more and make the leak worse. Use CRC electronics cleaner (quick dry) as it's gentler on rubber parts.
You could remove the distributor from the head and clean out the inside of the housing via the oiling slits, then put in a few drops of ATP AT-205 Re-sealer along with half an ounce of fresh oil, if the seal still has any integrity you might be able to revitalize it a bit, maybe.
If the leak gets too bad the best option is to buy a new or rebuilt distributor IMO.
The leak could come from a couple of sources IME; first is a bad rotor shaft seal which is located beneath the reluctor ring (the thingy with the teeth on the shaft). That seal is essentially not replaceable, at least not easily because the pinion gear on the engine side of the distributor is pressed on to the rotor shaft. Most other distributors have that gear pinned on and it can be removed easily, not so for our distributors.
One other possible cause of the leak, if the source does not seem to start from below the reluctor ring, is if you have a large oil leak from the O-ring or the valve cover, and you have a lot of oil blowing around the distributor it might get past the distributor cap "packing" (rubber gasket) or maybe if there is a very large leak it might get blown into the breather hole located on the top backside of the distributor housing. The oil pattern under the cap should give you some clues as to the source.
But again, if you see oil around the shaft at the bottom of the housing (internally) where the shaft dives into the distributor housing, as in the photos above, it is a bad shaft seal which is essentially not replaceable. If you do take the distributor apart (press off the pinion gear) that seal is not available as a separate part from anyone.
You would have to find a replacement rotary shaft seal, and no one makes that exact same size or design. The closest I found is a slightly shorter seal that should work, but may not last as long as the original as the sludge and grit from the old cooked oil that gets trapped inside the housing can get right up to the lips of that seal. The OEM distributor seal is better protected due to a unique shielded triple lip design.
There is also a shaft bearing that receives it's lube via oiling slits located in the narrow part of the housing that sits inside the head. So if you have oil getting past the seal you also have oil getting past the (single) seal on the bearing. This bearing is also a unique design, but a standard size, so there are substitutes that will work.
So what to do? First, do NOT use carb cleaner when cleaning off the old oil from inside the distributor, that can damage the seal more and make the leak worse. Use CRC electronics cleaner (quick dry) as it's gentler on rubber parts.
You could remove the distributor from the head and clean out the inside of the housing via the oiling slits, then put in a few drops of ATP AT-205 Re-sealer along with half an ounce of fresh oil, if the seal still has any integrity you might be able to revitalize it a bit, maybe.
If the leak gets too bad the best option is to buy a new or rebuilt distributor IMO.
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