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Old 10-03-2012, 01:17 PM
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Originally Posted by My 39 Buick View Post
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?
That's a good way to test it and it is telling you the can's no good if it won't hold vacuum.

Crane has an adjustable vacuum advance can kit- p/n 99600-1 that has the limiter plate, springs and an adjustable vacuum advance can including tool.

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.

Most adjustable vacuum cans will have a hex-shaped end where the vacuum port is located. Non adjustable cans are round.

More on timing can be seen here.

Until you get a timing light on it, put the line back the way it was. The link above has info on making a timing tape if you don't have a dial back timing light along w/other links at the bottom of the page.

Good luck.
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