Rochester Quad 800 questions
Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
Rochester Quad 800 questions
I just received this carb today. Does anyone know what this is and does it need to be plugged into a vacuum port?
Red arrow is pointing at it:
Thanks in advance.
Red arrow is pointing at it:
Thanks in advance.
Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
Thanks for the info. Can the vacuum port for the secondary plug into another vacuum port that is not being used on the carb it self or do I need to "T" it off pvc line or something? FYI, this is stage 2 rebuild carb from Jet-P.
Last edited by jackwabbit703; Mar 18, 2013 at 07:42 PM.
Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
[QUOTE=Shark Racer;1583399570]I believe I found another picture of that - is there an extra port?
The smaller inlet (which is pointing 90 degrees up in your picture) is connected via vacuum tube to a vacuum port right next to brake booster vacuum line on the back side bottom of the carb, right above the intake manifold. My older carb has the vacuum diaphragm and valve mechanism in the right front of the carb so, this one threw me off a little.
The smaller inlet (which is pointing 90 degrees up in your picture) is connected via vacuum tube to a vacuum port right next to brake booster vacuum line on the back side bottom of the carb, right above the intake manifold. My older carb has the vacuum diaphragm and valve mechanism in the right front of the carb so, this one threw me off a little.
Last edited by jackwabbit703; Mar 19, 2013 at 11:13 AM.
Race Director
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From: San Jose CA
I honestly have no idea what the big port is for - does it pull vacuum when you hook something up? The smaller port has a measured restriction in it to delay the relaxation of the choke/secondary blockoff when vacuum drops.
I'd drop Lars a note to be sure.
I'd drop Lars a note to be sure.
Last edited by Shark Racer; Mar 19, 2013 at 11:58 AM.
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Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
Thanks
Race Director
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that setup is shown in Cliff Ruggles book on the Quadrajet. The diaphram has two functions one to keep the secondary air valve from opening at cruise and idle and the second to act as a choke pull off. From this description I would say the choke will not crack open once the engine is started unless you attach a vacuum source.
Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
that setup is shown in Cliff Ruggles book on the Quadrajet. The diaphram has two functions one to keep the secondary air valve from opening at cruise and idle and the second to act as a choke pull off. From this description I would say the choke will not crack open once the engine is started unless you attach a vacuum source.
I will also look to see if there's an adjustment in the SAV.
Thanks.
Last edited by jackwabbit703; Mar 19, 2013 at 03:21 PM.
Race Director
Joined: Jan 2000
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From: San Jose CA
I think you may be on to something.
A simple test would be to apply vacuum to the diaphragm via the small port with the large "port" uncapped and verify that it holds vacuum.
I'm betting bpassmore is right, that the port is for adjustment of the arm.
Thread Starter
Racer
Joined: Feb 2013
Posts: 386
Likes: 3
From: Clifton Virginia
Thanks