74 Vacuum advance
Thread Starter
8th Gear
Joined: Feb 2009
Posts: 8
Likes: 0
From: Newnan Georgia
74 Vacuum advance
I'm replacing the stock Carter/Holley carb with a new Edelbrock on the stock manifold. The new carb doesn't have all the same vacuum ports, and I also have a vacuum advance solenoid mounted on the right-front side of the intake manifold, which connects between the carb and the distributor vacuum advance. According to the service manual, the solenoid is supposed to shut-off vacuum to the carb when the ignition is off, which doesn't seem to make sense to me because you don't have vacuum when the engine is off anyhow. I'm thinking I can eliminate this solenoid and connect the vacuum advance from the distributor directly to the carb vacuum port. Does anyone have advice or agree/disagree?
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
That solenoid is there to completely close the throttle plates when the ignition is turned off to prevent dieseling. If you've removed the smog stuff it most likely is not needed any longer.
Those are great solenoids to use in cars that have A/C to boost the idle speed when the compressor kicks in. You rewire it to the compressor so when you turn on the A/C it energizes the solenoid and boosts the idle a little to prevent the engine from stalling.
Those are great solenoids to use in cars that have A/C to boost the idle speed when the compressor kicks in. You rewire it to the compressor so when you turn on the A/C it energizes the solenoid and boosts the idle a little to prevent the engine from stalling.
Racer
Joined: Nov 2006
Posts: 259
Likes: 145
From: Missouri City Texas
You may consider using "manifold" vacuum, not "ported" vacuum. I have an Edelbrock Thunder series carb and performer EPS intake on an L-82. I'm running the vacuum advance from the manifold fitting with much better results than using ported vacuum. If you are interested, look under the Timing and Vacuum Advance section on: http://lbfun.com/Corvette/Tech/vettetech.html
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
You may consider using "manifold" vacuum, not "ported" vacuum. I have an Edelbrock Thunder series carb and performer EPS intake on an L-82. I'm running the vacuum advance from the manifold fitting with much better results than using ported vacuum. If you are interested, look under the Timing and Vacuum Advance section on: http://lbfun.com/Corvette/Tech/vettetech.html
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Paul 74 is probably world's leading expert on this stuff, I see he's on the scene.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
But whatever, we still do not know what carb we are speaking of. Manifold vacuum (yes I used last year) can differ from one unit to another.
Last edited by Paul L; Mar 31, 2010 at 05:41 PM.
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Thread Starter
8th Gear
Joined: Feb 2009
Posts: 8
Likes: 0
From: Newnan Georgia
Ok, now I'm really confused. I looked at Eckler's and Corvette Central site for a replacement solenoid and they call it a TCS solenoid (as you said) but note that it is for a manual transmission, and I have an automatic tranny!!
To answer your question I'm replacing the stock carb with a Edelbrock 1400, which is set up for EGR valve that I have, and also has a "ported vacuum" outlet and a "manifold vacuum" outlet. The manual says the solenoid allows the vacuum advance to be vented to the atmosphere when non-energized and vacuum applied to the vacuum advance when energized. Just wondering if this is really necessary and I should replace the solenoid (since I don't think it is working anyhow), or can I just connect the vacuum advance hose directly to the carb (either ported or manifold vacuum).
Sorry I forgot to mention I'm using the stock manifold with the Edelbrock adapter plate.
To answer your question I'm replacing the stock carb with a Edelbrock 1400, which is set up for EGR valve that I have, and also has a "ported vacuum" outlet and a "manifold vacuum" outlet. The manual says the solenoid allows the vacuum advance to be vented to the atmosphere when non-energized and vacuum applied to the vacuum advance when energized. Just wondering if this is really necessary and I should replace the solenoid (since I don't think it is working anyhow), or can I just connect the vacuum advance hose directly to the carb (either ported or manifold vacuum).
Sorry I forgot to mention I'm using the stock manifold with the Edelbrock adapter plate.
Last edited by RAStratton; Mar 31, 2010 at 06:05 PM.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 99
From: Ontario
Ok, now I'm really confused. I looked at Eckler's and Corvette Central site for a replacement solenoid and they call it a TCS solenoid (as you said) but note that it is for a manual transmission, and I have an automatic tranny!!
To answer your question I'm replacing the stock carb with a Edelbrock 1400, which is set up for EGR valve that I have, and also has a "ported vacuum" outlet and a "manifold vacuum" outlet. The manual says the solenoid allows the vacuum advance to be vented to the atmosphere when non-energized and vacuum applied to the vacuum advance when energized. Just wondering if this is really necessary and I should replace the solenoid (since I don't think it is working anyhow), or can I just connect the vacuum advance hose directly to the carb (either ported or manifold vacuum).
Sorry I forgot to mention I'm using the stock manifold with the Edelbrock adapter plate.
To answer your question I'm replacing the stock carb with a Edelbrock 1400, which is set up for EGR valve that I have, and also has a "ported vacuum" outlet and a "manifold vacuum" outlet. The manual says the solenoid allows the vacuum advance to be vented to the atmosphere when non-energized and vacuum applied to the vacuum advance when energized. Just wondering if this is really necessary and I should replace the solenoid (since I don't think it is working anyhow), or can I just connect the vacuum advance hose directly to the carb (either ported or manifold vacuum).
Sorry I forgot to mention I'm using the stock manifold with the Edelbrock adapter plate.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
