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Topic: Q-Jet vac port

in Forum: C3 Fuel, Emission Control, and Exhaust Systems

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Q-Jet vac port (1/9)
4/8/07 7:27pm

Silver69
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Joined: 1/26/2004
Posts: 313

Can someone identify the vacuum port that is pointed out by the arrow? Should this be plugged or does it have a hose attached. This is on a 69BB with a 4MV carb.Thanks Carb pic

(large image changed to link)Adams' Apple2007-04-08 18:20:12

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Q-Jet vac port (2/9)
4/8/07 8:02pm

Ten15
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East Hanover, NJ - USA

Vette(s):
'68 Black Conv. Matching 327/300 4 Spd. P/S, P/B, P/W, Tele, A/C

Joined: 9/25/2004
Posts: 525

Charlie,

On my '68 (which has a '69 7029207 Q-Jet) that port has a short piece of rubber that connects to the steel vacuum advance line that goes to the distributor.

Anthony

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Q-Jet vac port (3/9)
4/8/07 8:16pm

wetvet
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Lake Oswego, OR - USA

Vette(s):
1972 Steel Cities Gray T Top. Original Owner, Original Paint and Interior. The running gear has been rebuilt. only 250,000 miles on the clock..

Joined: 10/17/2003
Posts: 553

On my 72 carb (7042202 Q-Jet) this port has a vacuum line that goes to the vacuum storage tank, which is under the vacuum booster of the brake master cylinder. FYI. On the passenger side of the carb, next to the choke vacuum dashpot. That port connects to my distributer vacuum advance.
Hope this helps. Smile

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Q-Jet vac port (4/9)
4/8/07 8:22pm

Silver69
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Joined: 1/26/2004
Posts: 313

Thanks, the way mine is setup, my vacuum advance plugs into the vac port shown here with arrow. I'm confused now. I just had the carb rebuilt and it was off the car for awhile, but this is how it has always been setup. Could it have always been wrong? Vac. Line

(Large image changed to link)Adams' Apple2007-04-08 18:22:58

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Q-Jet vac port (5/9)
4/8/07 8:24pm

That is the correct port for the vacuum advance.

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Q-Jet vac port (6/9)
4/8/07 9:09pm

eddie20875

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Lanoka Harbor, NJ - USA

Vette(s):
1975 metallic blue coupe with t-tops,L48, t/t steering, black leather interior. 1990 L98, white/red leather interior, auto,a/c

Joined: 12/21/2006
Posts: 828

i know you have a bb but on my 75 the port you showed in the first pic is where my vacuum advance goes but that is on a sb 350. should be a vacuum diagram in the service manual.

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Q-Jet vac port (7/9)
4/8/07 10:19pm

Ten15
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East Hanover, NJ - USA

Vette(s):
'68 Black Conv. Matching 327/300 4 Spd. P/S, P/B, P/W, Tele, A/C

Joined: 9/25/2004
Posts: 525

Charlie,

I think that the port shown in pic #2 is for the A.I.R. system diverter valve.

If you had the original steel vacuum line, it will line up with the port in the front of the carb (pic #1).

You can see the line in a pic from any of the major suppliers.

Anthony

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Q-Jet vac port (8/9)
4/8/07 10:40pm

Silver69
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Joined: 1/26/2004
Posts: 313

[QUOTE=Ten15]Charlie,

I think that the port shown in pic #2 is for the A.I.R. system diverter valve.

If you had the original steel vacuum line, it will line up with the port in the front of the carb (pic #1).

You can see the line in a pic from any of the major suppliers.

Anthony

[/QUOTE]

You are absolutely correct. I was looking at a Doc Rebuild catalog and they have each year diagramed by engine size and HP. Very good diagram. So I will be getting the steel tubing and the new hoses.

Thanks for all the input guys.

Silver692007-04-08 19:41:28

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Q-Jet vac port (9/9)
4/8/07 11:00pm

2 cruzn

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Poquoson, VA - USA

Vette(s):
73 Conv, Blue-Green/White Top - 454, M21 - Dark Saddle Leather, Power Windows, A/C, Tilt/Tele, AM/FM St. (orig. and sounds like it too).#2 -- 2007 Coupe,3 LT package, Z51 option, Victory Red, Ebony Int. Clear Top.

Joined: 11/20/2004
Posts: 1023

[QUOTE=WETVET]On my 72 carb (7042202 Q-Jet) this port has a vacuum line that goes to the vacuum storage tank, which is under the vacuum booster of the brake master cylinder. [/QUOTE]

My '73 BB goes to the same place as WETVET... to the vacuum canister.

Ooops.. too late ... good info on Dr. Rebuild... Big%20smile

2 cruzn2007-04-08 20:02:56

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