Vacuum port on intake manifold

[Fishfan]

Hey guys,

318 Poly. 66 Polara. Just curious about this vacuum port on the intake manifold. The pic is from my old manifold, which I replaced with one suitable with my new 4-bbl carburetor. The "new" manifold has this port as well. I'm away from the car for the moment. I believe the vacuum line goes through the firewall and suspect it's for the AC/Heater.

 

[Toolmanmike]

Maybe someone else will comment but I have never seen anything connected to that port. It is always plugged. You would want the power brakes to hook up to the base of the carb .

 

[Fishfan]

Maybe someone else will comment but I have never seen anything connected to that port. It is always plugged. You would want the power brakes to hook up to the base of the carb .

Correct. And that's where I have it.

 

[Fishfan]

Maybe someone else will comment but I have never seen anything connected to that port. It is always plugged. You would want the power brakes to hook up to the base of the carb .

I need to chase it down through the firewall and see what it's connected to. I suspect AC. But nowadays my AC functionality is down to one button. I don't have any of the functionality that's supposed to be vacuum operated (fresh air door, etc).

 

[jimmyessbee]

That's where I draw vacuum for power brakes. On my 361, there is a port on it for the vacuum line for the heater control as well.

 

[MrMoparCHP]

There is a fitting that goes there if you have power brakes and/or AC

Alan

 

[Fishfan]

There is a fitting that goes there if you have power brakes and/or AC
View attachment 566291



Alan

The vacuum line that comes out of mine is of a tiny diameter compared to yours. Goes into the firewall.

 

[Toolmanmike]

There is a fitting that goes there if you have power brakes and/or AC
View attachment 566291



Alan

The original carbs must not have had a vacuum port in the back for brakes. Thet is a lot of vacuum pulled off of one port.

 

[Boydsdodge]

All types of fitting sizes with multiple smaller male fittings depending on the options of the car.
Large center fitting for power disc brakes, smaller will feed emisions, HVAC, or vacuum gauge. Etc...

 

[jimmyessbee]

The original carbs must not have had a vacuum port in the back for brakes. Thet is a lot of vacuum pulled off of one port.

Nah. The hvac port is tiny. Very little vacuum required there. It's really only for brakes and that hvac port is secondary. I don't want to speak too loudly because I'm not sure if it's true, but I really cannot ever recall power brakes powered by a port on the carburetor. But it is true that most of my machines have always been older.

 

[MrMoparCHP]

The vacuum line that comes out of mine is of a tiny diameter compared to yours. Goes into the firewall.

It is there to the right of the power brake hose in the picture (pointed at the throttle cable), just no hose on it at the time.


Alan

 

[Fishfan]

 

[Fishfan]

All types of fitting sizes with multiple smaller male fittings depending on the options of the car.
Large center fitting for power disc brakes, smaller will feed emisions, HVAC, or vacuum gauge. Etc...
View attachment 566295View attachment 566296

If I were to cap it off, would you happen to know what NPT thread size the port in the manifold is?

 

[Snotty]

Power brakes vacuum port.

 

[Fishfan]

If I were to cap it off, would you happen to know what NPT thread size the port in the manifold is?

Not on my car.

 

[Fishfan]

Power brakes vacuum port.

My car didn't come with power brakes. It came with a one-bowl master cylinder and no booster. I upgraded to current 2-bowl setup, with a booster and the vacuum has always come from the carburetor since I put in.

 

[Toolmanmike]

My car didn't come with power brakes. It came with a one-bowl master cylinder and no booster. I upgraded to current 2-bowl setup, with a booster and the vacuum has always come from the carburetor since I put in.

Probably the best. It won't lean out #8 when you step on the brakes. LOL

 

[volksworld]

usually 3/8 pipe...the later cars used the carb base port for the pcv valve (probably wanted the vapors distributed equally rather than into one runner) so they moved the power brake to the other location

 

[CBODY67]

Many mid-'60s carburetors only had the one large vac nipple for the pcv valve hose, on the front. That ONE intake manifold runner was used as the vac source for power brakes (mainly), with different vac trees to support the hvac vac items and cruise control vac source. On some, the cruise control vac source came off of the vac supply fitting/check valve on the power brake booster.

GM started the use of a large vac nipple on the rear base of the carb for power brakes. Using the intake manifold runner for the vac tree fitting for the other items which used manifold vac to operate with. hvac, cruise control, etc. The vac tree types and number and size of hoses it would accept seem to be endless, by observation.

Using that ONE runner in the intake manifold for a manifold vac source also means a shorter length of hose to the brake booster, which means less money spent to get the car to the end of the assy line. Just 10 cents less factory cost than using a longer hose from the carb adds up quickly when you consider how many vehicles might be involved!

Enjoy!
CBODY67

 

[saforwardlook]

Restorations 521 has a really nice assortment of detail parts for our C bodies as well as other Chrysler products. At the bottom of page 26 they show some available vacuum nipples such as the one you will need. They used to have ones with even more smaller nipples on them but I am not seeing those any more.

This is a great source of a lot of hard to find parts anymore that make the difference between having a nice restoration complete down to the last details vs a more run of the mill one.

A site to bookmark in my view.

https://521restorations.com/c-body/?sort=featured&page=26