The oldtime method for checking a vacuum advance unit was to try to blow cigarette smoke through the vacuum nipple. If the smoke came out the other side, we trashed it and installed another one. Occasionally a new one right out of the box would fail the smoke test.

I'd try splitting a piece of 3/16" steel brake line tubing with a cutoff saw in a Dremel tool, wrapping it around the pieces of the advance unit, and sealing it with 5-minute epoxy.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!