I think FOG is right the rubber seal would do that and don't really think there could be anything else but corrosion from the aluminum from the distributor like BP said.
Had a few like that and just wiggled and pried to get them out.
Might hurt the distributor housing but what else can you do.
When we tried to adjust the timing it was just frozen and couldn't turn either way. Finally that broke loose and timed the engine but couldn't remove it. Never seen that before but thanks for the tips guys.
