Vacuum question

Baker7888

Master Mechanic
Dec 3, 2021
374
28
Maine
Hey guys i'm running an SBC with a manifold vacuum fitting (1 big nipple 1 small nipple), Running an edelbrock carb and HEI vacuum advance distributor and no emissions equipment whatsoever. I did keep the vacuum ball and heat system. Hoping someone can help me with vacuum routing/look over my plan and offer advice/opinion


-- I believe brake booster goes straight to manifold (big nipple)? Edelbrock has a big port on the back which is plugged.

-- HVAC system has 2 lines coming thru firewall (white and purple)
From manifold (small nipple) i have it Y'd out with 1 line to WHITE line and one to vacuum ball. Other side of vacuum ball goes to Purple line.

-- Then for the distributor i was gonna hook the vacuum canister to the carb passenger side port (timed advance)

Does all this sound correct or should i change anything? Have not fired the car up yet
 

mikester

Comic Book Super Hero
Mar 10, 2010
2,649
113
Small town NY
Hey guys i'm running an SBC with a manifold vacuum fitting (1 big nipple 1 small nipple), Running an edelbrock carb and HEI vacuum advance distributor and no emissions equipment whatsoever. I did keep the vacuum ball and heat system. Hoping someone can help me with vacuum routing/look over my plan and offer advice/opinion


-- I believe brake booster goes straight to manifold (big nipple)? Edelbrock has a big port on the back which is plugged.

-- HVAC system has 2 lines coming thru firewall (white and purple)
From manifold (small nipple) i have it Y'd out with 1 line to WHITE line and one to vacuum ball. Other side of vacuum ball goes to Purple line.

-- Then for the distributor i was gonna hook the vacuum canister to the carb passenger side port (timed advance)

Does all this sound correct or should i change anything? Have not fired the car up yet
Do you have AC ?
Mine is set up this way. Large manifold port goes to the booster. Small goes to a Y with one going to the transmission modulator and the other to the vacuum ball. Purple goes from the firewall to the ball and the gray goes to the inline water shut off. Advance comes off the carb base and PCV goes to the large port on the back of the carb.






1663783838596.jpeg
 
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Baker7888

Master Mechanic
Thread starter
Dec 3, 2021
374
28
Maine
Do you have AC ?
Mine is set up this way. Large manifold port goes to the booster. Small goes to a Y with one going to the transmission modulator and the other to the vacuum ball. Purple goes from the firewall to the ball and the gray goes to the inline water shut off. Advance comes off the carb base and PCV goes to the large port on the back of the carb.






View attachment 207364
Man first things first, nice engine bay. Looks amazing. Ok a little to unpack here. I do not have ac, auto trans, water shutoff or pcv.

Purple from firewall IS going to ball, so good there. Also big manifold nipple to booster so good there as well.

Does the rest of my setup sound ok?
 

mikester

Comic Book Super Hero
Mar 10, 2010
2,649
113
Small town NY
Man first things first, nice engine bay. Looks amazing. Ok a little to unpack here. I do not have ac, auto trans, water shutoff or pcv.

Purple from firewall IS going to ball, so good there. Also big manifold nipple to booster so good there as well.

Does the rest of my setup sound ok?
Thanks for the kind words.
What is the white line from the firewall going to ? And the purple ? I have heat only in my 81 coupe and I dont recall seeing any vacuum lines for the heat. Maybe I should go under the dash and look at that. I put all that crap in many years ago. LOL
 
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57 Handyman

Greasemonkey
Feb 6, 2017
247
63
Mikestar I second Baker7888's comment...nice engine! But add...immaculately detailed engine compartment!

With regard to purple and white vacuum tubing from firewall, if I recall correctly, white tube goes to a device/control for the heater; purple one goes to vacuum ball for the AC controls (see Mikestar's picture). The vacuum ball is needed to modulate and keep constant the vacuum that opens/closes the AC/heater actuator doors in the selected positions. The purple line is the main vacuum source and goes to the back of the AC/heater control in your dash. If you're experiencing only heater (floor) or defrostor (base of windshield) airflow that means either the actuator is malfunctioning or it is not receiving vacuum pressure to open/close the main door in the HVAC system. Hopefully, the problem is lack of vacuum which is easily resolved; however, if the actuator needs to be replaced that is a big job.

My recommendation is do an extensive search of "AC/heater vacuum lines" etc. on this site and any other sites you frequent. By and large, the information will have a common thread of facts that will help you understand the mechanics of vacuum controlled HVAC in our classic cars. Good luck!
 
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Baker7888

Master Mechanic
Thread starter
Dec 3, 2021
374
28
Maine
Thanks for the kind words.
What is the white line from the firewall going to ? And the purple ? I have heat only in my 81 coupe and I dont recall seeing any vacuum lines for the heat. Maybe I should go under the dash and look at that. I put all that crap in many years ago. LOL
Sorry I should clarify. The car was originally AC equipped. I am running all the original hvac stuff in the cab, and under the hold I am using a non-ac box and no AC equipment under hood/on motor.

Mikester I have the white (or grey) line going to manifold vacuum (this line also has a Y that goes to the ball) The purple line goes direct from firewall to the ball
 

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