Vac Advance Unit, Testing Options

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Is there a proper test for the dizzy vac adv unit? i.e., how many pounds vac and how long should it hold. Also, what about the retard side; the same?

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question.
Does the car idle ok when you pull the advance/retard hose and plug it?

You can drive the car without the canister...it just starts the advance faster or pulls the plates back (retard) sooner for emissions.

I am pretty sure (but I am certain I will be corrected if I am wrong) that the retard side only pulls the diaphram back from the advance position.
It sits at rest with no advance, so you would not be able to move it by applying a vacuum to the retard side....you would be able to hold pressure though.

RIch

It hasn't run yet, Rich. I'm finishing my first T4 rebuild and was checking the dizzy out when I noticed this. (IMG:style_emoticons/default/poke.gif) No one ever corrects you, Rich. BTW, I appreciate anyones help, right or wrong. TY

When I pulled on the advance side(I refuse to say sucked) the armature would move but it would not hold a vacuum. I can't squeeze the trigger fast enough to produce a measurable reading and it won't hold with my tongue, either. The retard side produces no movement at all. So it sounds as if it might be dead. Next question; is this part still available?

I probably have a couple good ones laying around. It should hold a vacuum for quite some time.

I'll check back with you after I get a pn off the dizzy. Thx

question.
Does the car idle ok when you pull the advance/retard hose and plug it?

You can drive the car without the canister...it just starts the advance faster or pulls the plates back (retard) sooner for emissions.

I am pretty sure (but I am certain I will be corrected if I am wrong) that the retard side only pulls the diaphram back from the advance position.
It sits at rest with no advance, so you would not be able to move it by applying a vacuum to the retard side....you would be able to hold pressure though.

RIch

Wrong. The retard pulls it down from the rest position, the advance pulls it up from the rest position. That way the idle is dropped with the throttle closed (timing retarded), and the timing advanced over time when the throttle is opened (adding to the mechanical advance). Neither side holds "pressure", only vacuum, which isn't measured in PSI, but in inches of mercury.

The Cap'n

So it should move the arm when vacuum is applied to retard side as well, which it does not. Thanks for the tip as to how to ident one. BTW, vacuum can and is measured in inches. FYI, it's about a 2 to 1 ratio. 10psi = 20.36 inches merc. Ever ask yourself why someone would use mercury as opposed to water? Anyway, I have both styles of manometers so if you know an exact value I could use it. TY

I had wrong vac. units in cars already. Be sure to cross reference it. The tech tips 700? lists which ones goes with which distributor. Rich at High Performance house might have a NOS one for you.

And was there any noticeable differences between the different vac canisters. Weren't these referred to as dashpots once upon a time?

[914_teener]

The Cap'n
[/quote]
So it should move the arm when vacuum is applied to retard side as well, which it does not. Thanks for the tip as to how to ident one. BTW, vacuum can and is measured in inches. FYI, it's about a 2 to 1 ratio. 10psi = 20.36 inches merc. Ever ask yourself why someone would use mercury as opposed to water? Anyway, I have both styles of manometers so if you know an exact value I could use it. TY

I believe the values are listed on the Pelican Board for the different dizzes for the Tech Article for timing our cars.

BTW....I am interested in this post as I believe a have a problem with mine as well. I am wondering with some parts becoming difficult to find. Why run it?

My car will never be smoged as it is a 73.

What are the disadvantages if any? No hijack intended.