While troubleshooting an ignition problem i discovered the vacuum advance on the dist would not hold vacuum. I replaced it with another correct vac advance I had which holds vac and whose arm moves when vac is applied. I installed it on the dist still in the car but when I apply about 13 "hg vac it holds but nothing in dist moves. Is this correct or does vac advance work only after centrifugal advance has tapped out around 3,500 rpms? I hesitate to use more vacuum for fear of rupturing the diaphragm in the unit. Any comments are greatly appreciated.

 

The plate or whatever that is supposed to move is frozen in place. Dismantle and free it up...Check that you can easily move the plate manually. Had a car once where the whole advance mechanism froze - acceleration figure went out to hours, as you could only apply throttle in .001" increments without it choking.
jp 83 Euro S AT 53k

 

Thanks, wondering about that. I am able to set timing correctly at 3000 rpm and at idle--just did it. I am also able to move plate or whatever by hand, I think, but will check again. I have an old distributor that I'll reassemble and see if it works differently. If you are correct I hope this is the source of my problem where after 20 minutes of driving with plenty of power, etc she starts to stumble, back fire and stall when I stop with tach gyrating only to start again and stumble intermittently on the way back home over and over again.

 

Vacuum advance plate was frozen, distributor shaft wobbly--replaced with another dist. I had-- no good, problem persisted. Replaced spark box with a good used one--problem solved. The car is running strong...for now.