Diverter ports on Edelbrock 1902 quadrajet

[howzzzit]

Anyone know what the diverter ports are used for? Check the one on the pass side and it has vacuum at idle. Odd because it's half way up the side of the carb well above the throttle plates. Maybe tunnels downward inside the base. Currently capped. Just wondering.

Thanks

[HotWheelsFan]

Carb vacuum ports vary to what uses them by year and vehicles they are used on. But yes, the vacuum supply originates below throttle plates and may also connect to the primary metering rod plunger.

Bob

[geezer#99]

Choke pull off hooks up there.
It’s a manifold vacuum port.

[howzzzit]

Assume it would work to set idle mixture with a vacuum gauge?

[geezer#99]

[QUOTE=howzzzit;9259643]Assume it would work to set idle mixture with a vacuum gauge?[/QUOTe

Yup!
Any manifold vac source works for that.

Why isn’t it hooked to the choke pull off?

[howzzzit]

A is the diverter valve I'm talking about and B is the choke pull down and it's connected. Just wondered because A is so high on the carb I didn't think it would have manifold vac, but it does.

[geezer#99]

Well as I recall A is connected to the baseplate and is open to the plenum. It was normally used for the charcoal canister vacuum source.

[howzzzit]

I thought the canister used ported vacuum? A port has vacuum at idle.

[geezer#99]

Just curiousty, but why do you call it a diverter valve?

[howzzzit]

In the picture Edelbrock calls it a diverter port. I did accidentally refer to it as a valve.

[geezer#99]

Maybe that’s what edelbrock calls the canister.

[Rust_never_sleeps]

On my Rochester, that port supplies manifold vacuum to this sensor in the air cleaner.
It sits below the primary throttle blades, so seems consistent with what others have said

[RichardJ]

https://8c68fba3fc.nxcli.net/wp-cont...Carburetor.pdf

Most of the time, Edelbrock is just as confused, mixed up and indecisive as to which port should be used for the Distributor Vacuum Advance Port. In this case they seemed to have decided that Ported Vacuum should be used for Vacuum Advance. Port H is clearly indicated.

In keeping with the original topic, there is a second "A -Diverter Port" on the rear of the carb. Using Edelbrock's own Search feature, they don't seem to know what a Diverter Port is either.

A.I.R. Systems use a Diverter Valve. There were several variations of the AIR Systems through the years. so that may explain the two different ports.

[HotWheelsFan]

What connects to the various vacuum ports depends on the vehicle or application.

There are 1000's of different vacuum routings for vehicles and only dozens of carb to supply the vacuum.

Of course each vehicle has its needs and if the carb is not stock the the vehicle, use your best judgement as to the best ports to use for each need.

Most carbs will have the same similar sources for vacuum. Manifold vacuum - is manifold vacuum no matter which port supplies to. Where the placement of the port is, and its fitting size makes an easy guide as to what to use each port for.


Not trying to contradict anyone, just saying an carb not original to the vehicle has no absolute schematic to the use. For instance: the same carb could be used year after year when the application may have different needs such as being used for a vehicle before added smog devices - and then through the years of smog devices being added to vehicle. An aftermarket carb could remain the same, but a certain vacuum port may have a different use intended.


For street use a carb should have a choke pull off and I have seen different ports used to supply the vacuum. This is definitely an item needed for drivability and should be hooked up to manifold vacuum, regardless of the port used to supply it.

Bob

[howzzzit]

Thanks everyone. You're right about Edelbrock's customer service. What customer service? Was on hold over 15 minutes yesterday. Kept saying I was next in line. The guy on the other end either went to lunch or another customer had a heck of a problem. I hung up and sent an email. Received a reply that I would be contacted by email within 8 days!!!

[dmjlambert]

I used a small slip of paper to find out which port was ported vacuum on my Quadrajet. The paper stuck to the port at RPMs above idle, and fell off at idle.