this is great to know, unfortunately i can feel no adjustment screw inside vac can...... And the motor is not running/no vacuum source.

1955 tbird 

It should move when you suck on it, try Steve's suggestion see if it has an adjustment. While you have it in your hand maybe you want to modify it so you shorten your timing a bit and also you could try fit Mr Gasket D925 springs as well...? Jus' sayin'..



"Came too close to dying to stop living now!"

Those Mity Vacs are only $40 or less on Amazon. Put a vacuum gauge in the car, check your vacuum at cruise. You can then duplicate rpm and vacuum at the dizzy, and check your total running advance. With a second set of hands and eyes, you can plot the vacuum curve by inches. Really helps when tuning. Bleeds brakes real well, too.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Many of the vacuum pots are adjustable - it takes a 3/32 Allen wrench - that is long enough to reach down directly through the vacuum port. To limit the amount of vacuum advance on those units, you turn the Allen screw inside to preload the diaphragm spring. It could be - that your unit has the preload set-up pretty tight already - and therefore takes a good bit of vacuum to make it move the arm. The direction the screw is turned to tighten it - is not the intuitive direction. You must turn them CCW (counter-clockwise) to increase the spring loading.
Can you run the engine as it sits now? And then use the existing manifold vacuum as a test source? I have a '74 Olds I use as a vacuum donor when testing the pots......................


 
 Steve Metzger       Tucson, Arizona

Motorcraft part # 12127

1955 tbird 

Hi, I recently bought a Cardone part # 30-2808 distributor for 1957 and later block. I hooked a vacuum hose to the advance diaphragm to check
operation before installing. (I'm replacing my 1955 load-a-metic distributor). The advance arm from vacuum can would not move even though the advance 
plate in the distributor is free. I provided as much suction as possible using my mouth. I removed the diaphragm from distributor and again tried to actuate the arm while sucking on the vacuum hose. I couldn't get it to budge. Its seems as if there is a very tight spring under the diaphragm and it takes a huge amount of 
pressure to overcome. Does this distributor require some centrifugal advance to kick in before the vacuum will pull the diaphragm / arm ?? Anybody with experience with this distributor care to chime in? Thanks in advance,  Brett

1955 tbird