a little more info here please!
"When you connected the vac advance to the manifold source did the engine idle up? If not then it's likely the vac canister is ruptured internally causing a vacuum leak that is noticeable when connected to a manifold source. When it's connected to a ported source it's not so noticeable. So first things first, get a timing light, then test the vacuum advance unit, if it's ruptured get a replacement."
While reading here about the ruptured diaphram it dawned on me that my vac can really has no function. I have set and reset the timing on my bare bones 350 and ported and manifold vac does the same thing. Dosent really change my timing. That being said, i removed the vac can and applied or tried to apply vaccume presure using a mighty vac tool and i can not get any presure to hold in the can. Translating to no movement of the adjusting rod. Is this a good method for checking these cans?
Question 2 is, I have read that these cans can be adjusted with an allen wrench. Is this true for stock factory made cans? The one i just removed does not appear to be adjustable in any way.
This is all new to me and i have been head scrathing since i started tinkering with this car! So needless to say any and all help will be greatly appreciated.