quadrajet vacuum line woes

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Jmattsen

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Jacob
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1981
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C20
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After rebuilding my quadrajet my truck runs even worse than it did before (which was pretty ******.)

i tried my best at eliminating all the unnecessary stuff like the delay valve and the check valve to keep everything simple but now i am having a nightmare of a time finding some consistent information on what vacuum lines i need and what ones go where.

after a couple hours online this is what i have came up with.

Manifold port goes to the brake booster

Front right port goes to the distributor advance

Front left gets capped

Lower front goes to the pcv valve


Correct?

and for some stupid questions...

on the carb, what does the "rear vacuum brake assembly" and the "front vacuum brake assembly" do and where should i hook up their lines to?

i swapped out the electronic choke for a manual one, do i have to do anything more than pop the cap off and swap it out or is there another step i missed involving vacuum lines or electronics?

below is the diagram off of the front of my truck, can sombody point out where the brake booster is supposed to be?

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thanks in advance:whymewhyme:
 

Quadrajet Power

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Make sure your choke assembly doesn't have an open port. If it was hot air originally and converted to electric, it will pull vacuum, so cap off any ports if it has one.
And cap off any port that you don't use, even if it doesn't pull vacuum at idle, it will pull vacuum at part throttle.
Hope this helps some.

Send me your email and I can send a couple of documents I am working on that might help also.
 

Jmattsen

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So now that I'm looking at it I don't even have the same vacuum ports as the page I got this information from. I have one on the manifold, one on the front center above the fuel filter, one on the front left below the fuel filter and one on the back....

And I am pretty sure my brake booster does not have a vacuum port on it anywhere, at least not that I can see
 

Jmattsen

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Location
Seattle
First Name
Jacob
Truck Year
1981
Truck Model
C20
Engine Size
305
Make sure your choke assembly doesn't have an open port. If it was hot air originally and converted to electric, it will pull vacuum, so cap off any ports if it has one.
And cap off any port that you don't use, even if it doesn't pull vacuum at idle, it will pull vacuum at part throttle.
Hope this helps some.

Send me your email and I can send a couple of documents I am working on that might help also.


Messages sent, thanks for the help
 

Quadrajet Power

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I sent the documents. Hope they help.
If the port on top center is large, that is a vent port for exhaust vapor and was connected to the charcoal canister.
 

suburble

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Don't know how you may have capped / looped / eliminated stuff, but are you sure the EFE valve in the exhaust is open? I accidentally looped mine to vacuum when I was playing with emission stuff trying to isolate carb issues, and it barely ran.

-Josh
 

suburble

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Also, you might want to play with your timing now that you have unhooked a bunch of stuff.

-Josh
 

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