Vacuum advance not working on dizzy. Now what?

Engine, Transmission and related drivetrain.
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Button
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Vacuum advance not working on dizzy. Now what?

Post by Button » 02 Dec 2019 12:02

Hey guys, I just got insurance and registration on my car today so I am trying to get it tuned properly now that I can drive it. I checked the vacuum advance with a vacuum gauge and it it won't hold at all. This is on a Matchbox distributor. Is it worth trying to replace the diaphragm or should I just find another distributor? Does anyone make a new replacement matchbox distributor or do need to find a used one?

I have a standard dizzy with pertronixs and working vacuum advance. I guess I will throw that on for now but I would prefer to run a matchbox dizzy.

Thanks

Chris

Button
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Re: Vacuum advance not working on dizzy. Now what?

Post by Button » 02 Dec 2019 14:52

Well, i hooked a vacuum up to the nipple and it wouldn't hold but when testing the distributor with a timing light the timing advances as I give it gas so I guess it is working. Hmmm

datzenmike
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Re: Vacuum advance not working on dizzy. Now what?

Post by datzenmike » 02 Dec 2019 19:37

What you are seeing is mechanical advance. It increases with engine speed.

Vacuum advance is engine load dependent. Light load (high intake vacuum) the distributor advances. Heavy throttle (low intake vacuum) the advance drops.

Make sure that the hose to the advance canister is not cracked or leaking first. I just suck on the end and watch the distributor advance.

Take the vacuum advance off the points distributor and put on the matchbox.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs

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RMS
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Re: Vacuum advance not working on dizzy. Now what?

Post by RMS » 02 Dec 2019 19:50

I thought those cans would inter change
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

Button
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Re: Vacuum advance not working on dizzy. Now what?

Post by Button » 03 Dec 2019 14:36

Thanks Mike, makes sense. I tested the hose on the other distributor and it held so I think it's good. Out of curiosity what is the downside of not running the vacuum advance

RMS are you saying they are or are not interchangeable?

Thanks

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bertvorgon
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Re: Vacuum advance not working on dizzy. Now what?

Post by bertvorgon » 03 Dec 2019 14:50

They should inter-change, at least I have done that in the past.

http://www.superchevy.com/how-to/additi ... ion-timing

You should try to get your vacuum advance running on a street motor.
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Button
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Re: Vacuum advance not working on dizzy. Now what?

Post by Button » 03 Dec 2019 17:06

Great articled Keith. In the article they talk about ported vs. direct source vacuum saying that direct is better. Probably a dumb question but on an L20 with the Weber 32/36 where is a direct vacuum port? At the moment I have the vacuum advanced hooked directly to the carburetor. Is that correct? Also on the subject of getting the car tuned should I do a vacuum test to know what the vacuum is at?

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RMS
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Re: Vacuum advance not working on dizzy. Now what?

Post by RMS » 03 Dec 2019 18:24

that would be a tuned port on the weber. you will want to pull off the manifold but you will need a bsp fitting. no vacuum advance is fun but eats the fuel.

Are interchangeable.
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

Button
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Re: Vacuum advance not working on dizzy. Now what?

Post by Button » 03 Dec 2019 19:02

Thanks RMS. So I guess I will just remove the line for now and plug the port while look in to swapping the vacuum canister.

Cheers

Chris

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