Dual Diaphragm (vacuum advance/retard) Distributor

racerdaveMember

A question, did all Panteras (71-74) come from the factory with a dual diaphragm (vacuum advance/retard) distributor? And part of that setup is the Distributor Vacuum Control Valve (12A091), where was it mounted? The attached diagram shows it in the water tube above the thermostat, but I don't have a fitting for it in my water tube. I've been told if there is no boss in the water tube then the car never had a valve. And if it never had a valve, then it never had a dual diaphragm (vacuum advance/retard) distributor. But when I look in the Pantera Parts Manual, all they list is dual diaphragm distributors for Panteras. And they list a Distributor Vacuum Control Valve for 1971 through 74. My car is a 72 #3334 and I don't have the boss in the water neck, but I seem to remember a dual diaphragm distributor in the car when I got it, but that was 28 years ago.
So fellow Pantera owners, if you have (or had) a Distributor Vacuum Control Valve where is it mounted? I’m particularly interested in 1972 Pre-L cars. And what distributor came with your car? I think 1971 had a single points distributor and 72 had dual points, but was it dual diaphragm too? Thanks in advance for any information.

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6/25/079:22 AM

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jon3613Member

This is an image of the vacuum valve in the water pump boss. New water pump, but the same as the original. It has the dual diaphram type distributer with the dual points.
This is a 1972, s/n 3613.

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6/25/072:13 PM

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racerdaveMember

Thanks for the response Jon. I’ll need to hear from a few more car owners, hopefully someone with a lower SN# than mine. But I'm guessing only EGR equipped cars had the boss in the water neck because they added a second temperature controlled vacuum valve and there was no place else to put it. That 2nd valve is in the bottom of the picture and has just two vacuum lines.

6/25/073:25 PM

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crazydaveEFI Expert

I have a 74 and it came exactly as pictured. Even still had the Motorcrap carb on it. It also had a dual point dizzie.

6/25/077:42 PM

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George PAdmin.

Dave,

all US manufactured Clevelands were equipped with dual diaphragm dizzys throughout the 5 year production run from 1970 through 1974. This was part of the emissions controls employed in that era. Returning the vacuum/ignition system stock will not make your motor run better.

The diagram you posted is of a 1974 Pantera, which was equipped with EGR, something your car did not have. Your car would have been equipped with only one temperature controlled vacuum switch (TVS switch) for the distributor controls (called spark controls). The second TVS switch in the diagram is for the egr system, something your car doesn't have.

emissions wise, your '72 motor would have had 4 systems:

1. Positive crankcase ventillation
2. Evaporative emissions control (charcoal canister)
3. Heated air controls (air filter assembly)
4. Distributor controls (spark timing)

the single TVS switch in your car would be of the type with 3 nipples on it, and would have been screwed into the water pump, just as Jon has shown in the photograph.

Your '72 Cobra Jet also had a dual pont dizzy.

cowboy from hell

6/26/072:11 PM

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racerdaveMember

Thanks for the good information George. That straightens things out. Now my "dizzy" question no longer makes me dizzy