The Stovebolt Site Forums The Shop Area Engine Shop dist. luber

The lubricant cup on the distributor was used to the end of the run of the 235/261 engines (1962/63).

There is a spring another small part inside the cup's "stem" (a plug or a washer - a different part for different years - see links below).
Here is a diagram from the 29-54 Master Parts Catalog and slightly different diagram for 55-57 in the 29-57 MPC. (thank you, Keith Hardy).