How to hook up a vacuum gage on my 39 Desoto

[desoto1939]

OK this is something new to me.  My 39 Desoto does not use the vacuum line to run the wiper motor it is electric.

 

So basically, the only vacuum line that i have is a metal line at the bottom of the carb that runs to the vacuum advance unit and this is attached to the dizzy body.

 

So Do I disconnect the vacuum line at the base of the Carb and connect the Gage at this point to the carb or where else do i connect.

 

Any pictures or pointers would be helpful.

 

Want to try this method of setting the carb and adjusting the car. Have never done this want to learn.  Always willing to learn something new.  Also any recommendation on a Vacuum Gage

 

Rich Hartung

Desoto1939@aol.com

[Loren]

The vacuum line to the distributor is "Ported" vacuum and would not be suitable.

There should be an 1/8th inch plug on the manifold which would work for "Manifold" vacuum.

 

For cars with dual diaphragm fuel pumps designed to boost vacuum to the wipers, you can use the same port.

The vacuum diaphragm connects here on its "pressure" side (the vacuum side goes to the wipers). It's not really a pressure side or even an "exhaust" side. Its function is to use manifold vacuum to boost the pump on start up.

[desoto1939]

Loren:   Since I have an electric wiper motor the fuel pump is not a dual diaphragm it is a single diaphragm pump model AC 588, standard FP for alot of MoPar cars and trucks.

 

So i will have to look for the 1/8 inch plug in the manifold. I will let you know what I find. Hopefully the plug will come out without breaking since this is the original manifold for the car.

 

 

Rich Hartung

desoto1939@aol.com

[Dodgeb4ya]

Connect the vacuum gauge directly to the intake manifold..

Should be a plug on it to remove for a line fitting.

[Doug&Deb]

I concur with the port on the manifold. It should be behind the carb. It made it much easier to fine tune the carb on my Coronet. 

[desoto1939]

I found the plug near the base of the carb near the sisson choke assembly. The plug is basically a slotted plug and it looks as if it has never been removed.  I will have to put some BP Blaster on the threads to get the rust off the plug so that i can loosen the plug.

 

Nervous about trying to remove a plug in the manifold that has been installed over 80 years ago. My luck it will snap off.

 

Rich

[Doug&Deb]

A few taps with a hammer may break the rust bond. As always use patience.

[FarmerJon]

If you get car up to operating temp, spray it with PB blaster, tap on it, and lightly tighten it several times before trying to remove it, you may find it comes out with little trouble.

I will often spray bolts down several times, a week or more before trying to remove them.

[Sniper]

One trick for removing old fasteners is to tighten it a bit first, then loosen it up.  Just be patient and if you have a torch a little spot heat around the fitting might help too. 

 

One thing I like to do to prevent future issues with this sort of thing is to put a wrap or two of teflon tape on the fitting.  It will prevent future seizures.

Edited April 11, 2022 by Sniper

[soth122003]

Hey Rich,

Everyone seems to have you covered for the fitting so I'll recommend the Harbor Freight vacuum/Fuel pressure gage.

Been using mine for over 10 years and works like a champ every time.

 

Joe Lee