OK- - - -it sounds like you've got a hole in the diaphragm. Use a long piece of rubber tubing attached to the distributor line and suck on the end of the tube like a soda straw. The distributor should move, and if you plug the end of the hose with your tongue the dizzy will stay advanced. If not, you've got a holed diaphragm. The old school leak test was to blow cigarette smoke into a vac advance and see if the smoke came out the dizzy side.
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!