Vacuum Source

mikester

Royal Smart Person
Mar 10, 2010
1,901
113
Small town NY
Not sure what topic this should go under but I need some vacuum info.
I have a new heater valve. I know the gray vacuum tube from under the AC box goes to this. The purple one goes to the vacuum ball or canister depending what brand car you have. I have a ball and I also have the long style that I got off a Cutlass at the local yard.
Now, where does the feed for the ball come from ? The Holley on the crate motor has a large port on the rear base. The mainfold has a large fitting right behind the carb as you can see in the picture. Originally I was going to use that fitting for vacuum to the brake booster but instead of putting in a 90 degree fitting with a barb I put a T fitting into it instead so I could get vacuum from both sides. Theres also a port on the front of the Holley that I assume will be for the vacuum advance on the HEI.
In the end I need vacuum for the booster, the TH350 modulator, the vacuum ball for the heat/AC and something for the PCV valve.
What do you guys have set up ?
IMG_0981.jpg IMG_0979.jpg
 

79 USA 1

G-Body Guru
Sep 2, 2011
681
93
Cheektowaga, New York
On my 406 I have the PCV using the 3/8 hose port at the base of the carb. I purchased a inverted flare adapter to run the brake booster off the port in the manifold. I also drilled and brazed a piece of 1/4 inch tube with a hose flare in to the adapter to use as a vacuum port for the modulator on the transmission.
Not a great picture but just visible under the carb.

P1011881.JPG
 
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mikester

Royal Smart Person
Thread starter
Mar 10, 2010
1,901
113
Small town NY
On my 406 I have the PCV using the 3/8 hose port at the base of the carb. I purchased a inverted flare adapter to run the brake booster off the port in the manifold. I also drilled and brazed a piece of 1/4 inch tube with a hose flare in to the adapter to use as a vacuum port for the modulator on the transmission.
Not a great picture but just visible under the carb.

View attachment 169206
Basically you have the same setup as mine but I have the fitting thats a tee and will have two hose barbs. The one you can see will go to the booster, the other one thats not in yet will go to the modulator. Maybe I'll put another hose barb off the back if theres enough to drill into for the vacuum ball. I'll run the PCV off the same port on the back of the Holley.
My other question for you is do you know the brand of the carb linkage bracket you used ? I bought a Spectra from the local autoparts and it didnt fit right. The mounting hole was 3/8 and I have 5/16 studs on the GM manifold. It also didnt fit right over the ear of the carb. The 90 bend was in the wrong place. Ive got a modified Holley bracket on there now but after looking at your kickdown cable it doesnt look like mine is going to be in the right place.
 

565bbchevy

Geezer
Aug 8, 2011
8,027
113
Michigan
On my Regal I have the rear port on the carb going to the PCV and the manifold port near the back of the carb is for my brakes and since I have a vacuum canister for my brakes I used the port on there to supply vacuum to my AC/ heater controls and eliminated the plastic vacuum ball.
My Holley has 2 small ports up front one is for the distributor advance and the other is capped.
I also bought this style heater valve since I wanted new for the SBC.
1614128668950.png

I only use this style carb bracket for my Holley's, and you can mount a kickdown bracket to it.
1614130274683.png
 
Last edited:

79 USA 1

G-Body Guru
Sep 2, 2011
681
93
Cheektowaga, New York
My other question for you is do you know the brand of the carb linkage bracket you used ? I bought a Spectra from the local autoparts and it didnt fit right. The mounting hole was 3/8 and I have 5/16 studs on the GM manifold. It also didnt fit right over the ear of the carb. The 90 bend was in the wrong place. Ive got a modified Holley bracket on there now but after looking at your kickdown cable it doesnt look like mine is going to be in the right place.
If I remember correct it is a Mr Gasket linkage kit or Cal Custom (Yes it's that old) that I modified. I ended up adding a 90 degree piece of steel under the bracket at the carb stud to keep it from rotating when the throttle was depressed. Was a lot of trial and error but managed to make it work.

P1011880.JPG
 
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mikester

Royal Smart Person
Thread starter
Mar 10, 2010
1,901
113
Small town NY
On my Regal I have the rear port on the carb going to the PCV and the manifold port near the back of the carb is for my brakes and since I have a vacuum canister for my brakes I used the port on there to supply vacuum to my AC/ heater controls and eliminated the plastic vacuum ball.
My Holley has 2 small ports up front one is for the distributor advance and the other is capped.
I also bought this style heater valve since I wanted new for the SBC.
View attachment 169214
I only use this style carb bracket for my Holley's, and you can mount a kickdown bracket to it.
View attachment 169222
I looked at those brakets but they wont work with the AC high idle solenoid. I guess I'll have to modify the Holley bracket again. I love how these companies make stuff for specific uses and theyre not even close to being right. I had a thread about this months ago. Couldnt find a bracket for a Holley and a TH350 kickdown for a Vortec motor. Im glad I have a friend with a TIG welder. LOL
Older A-bodys used that intake port with a fitting that had ports for the brake booster, heater-A/C, and/or transmission.
Do you know what years ? The one yard I go to has at least 5 or 6 of them. Only thing is will that fitting clear the carb in the back ? Not much room under there.
 

565bbchevy

Geezer
Aug 8, 2011
8,027
113
Michigan
I doubt any factory vacuum T fitting will fit with a Holley carb (unless you have a tall spacer) since it hangs over and requires a low profile fitting, obviously not an issue with a Quadrajet.
 
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