67 Heating/AC Vacuum Source - Pontiac GTO Forum
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post #1 of 7 (permalink) Old 07-22-2018, 12:33 PM Thread Starter
 
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67 Heating/AC Vacuum Source

I am a ways away from needing this, but I have spent way too much time looking and haven't found it. Where is the engine vacuum source for the heater/AC control?

I have my engine running and all vacuum ports accounted for (i.e. transmission, dashpot, distributor vacuum advance) and I don't have any additional vacuum sources on my stock Rochester Quadrajet carburetor or stock manifold.

Before I did disassembly, the original vacuum connection from the hollow stud at the back driver's side of the carburetor had a vacuum line that went to the dashpot, but also had a "T" fitting that was cut and plugged. Is that the vacuum location for the heater/AC control and off of a factory "T"?

Thanks in advance.
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post #2 of 7 (permalink) Old 07-22-2018, 01:19 PM
 
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Your 1967 Service Manual does not show this? I did not look real close, but my 1968 Service Manual shows the heater/AC controls and would think it shows the source for the vacuum line. Again, I know sometimes they can show some things and be vague on others stuff.

Read on a 1967 Firebird website that the vacuum line came off the hollow carb stud on the passenger side. Guessing it would be the same for the GTO, but not 100%.
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post #3 of 7 (permalink) Old 07-22-2018, 09:01 PM Thread Starter
 
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The service manual just shows the diagram for the vacuum routing for the heating and AC, but all it shows is a line that says "to engine vacuum", but it doesn't say where.
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post #4 of 7 (permalink) Old 07-23-2018, 03:47 PM
 
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There are a few ways that this vacuum line is set up. It largely depends on whether you have an automatic or standard transmission and whether you have California emissions (Re; Air Pump) or not.
But in any case, page 442 of the "Pontiac GTO Restoration Guide" by Paul Zazarine and Chuck Roberts sheds a little more light on the subject. Still a little vague but helpful.
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post #5 of 7 (permalink) Old 07-23-2018, 10:22 PM Thread Starter
 
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Thanks Sixty7GTO. I have that book and must have missed that page.

My 67 is an automatic without an air pump. Based on that, it looks like it is a T off of the hollow vacuum stud like they had it when I first bought it. The routing for the 66 looks a little different than the 67, but I guess the concept is still the same.

Do you know if there are supposed to be any clamps between the T and where it connects at the firewall? If so, where?

Thanks again for your help.

Dan
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post #6 of 7 (permalink) Old 07-24-2018, 01:12 AM
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No clamps and it shouldn't connect at the firewall it should go all the way to the control.
The vac can on your box on the firewall should have two lines going to it.
Mine had the wrong can, single port like the door on the inside and all the hoses were wrong.
Check out this thread, there are 5 hoses and the control is numbered (see last post).
Engine vac comes off the hollow stud w/tee that attaches the carb and goes to the control through the 3 holed grommet in the firewall.

https://www.gtoforum.com/f83/66-gto-...94/index4.html

Diagram

https://www.google.com/search?q=1967...WTIotj8Ys8m9M:
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post #7 of 7 (permalink) Old 07-24-2018, 08:22 AM Thread Starter
 
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Thanks Goat Roper. I think I have it now.
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