Quadra-jet Connections-need help.

[dshanks]

Hi. Im currently working on the timing and vacuum, and I was wondering if I could get some assistance making all the correct connections to my new Quadrajet that I bought from Carburator Dr out of Canada...

The carb is not the same model at the one that came on my 71 4speed. It has an electric choke, and there are more vacuum ports than what mine had.

Ive tried to take detailed photos of the connections in question here.
these first 2 pics are of the front of the carb. I have labeled each port, there are 2 views with the same labelling.




Connection 1 is currently blocked off. Connection 2 is currently going to the PCV valve. Connection 4 is going to the Vacuum can (not sure exactly what it does) in the left fender.
I have been experimenting with connections 3 and 5 for use with the vacuum advance. I have a feeling this is what Ive read so many threads about "the big debate"?? But I really have no idea...
There is also a hose that you can see that goes from one fitting to another. The carb came like that and I haven't touched it. I figured it was there for a reason.

Also, can someone explain the different adjustment screws that can be seen on the bottom of the carb? I know the idle on the throttle arm, thats it...

Here is the fitting on the manifold, it goes to a splitter, then to the firewall and to the top fitting in the vacuum can. The fitting here on the back of the carb goes straight to the power brake booster.


Here is the electrical connection that went to the carb before


And heres the connection on the new carb


As always, thanks for all your help! If you have questions let me know!

Derrick

[Bill75]

Well, I might be able to help with some of the questions:
Here's a picture of the lines and where they go


The screws you mentioned on the bottom of the carb are the idle mixture screws, located on each side of the carb. They are adjusted equally for a smooth idle. In most cases about 5 turns out from seating. One method is to adjust them out about 5 turns then with the engine WARM turn them in until the engine starts to run rough, then back them out slightly until it's smooth. I'm sure someone else will chime in with a much better method.


The last view of the barbed fitting on the carb is for the electric choke thermostat. It needs to be hooked to a 12V source. If you don't have one picked out yet, the windshield wiper motor is a good one. It's easy to get at and it's only on when the ignition key is on.

Don't know what the connector is for, if it was on an electric choke before then one of the wires is 12V the other is most likely ground. If that's the case you could use that 12V source. Test it first with a volt meter to make sure it's the right voltage and is only on with the key.

Bill

[bobs78]

There's are diagrams of the hose connection on Dr. Rebuild's site. Here's a link
http://www.docrebuild.com/dr-r-web/SPARK-KITS.HTML I think this might help.

[Maymyvetteliveforevr]

There's are diagrams of the hose connection on Dr. Rebuild's site. Here's a link
http://www.docrebuild.com/dr-r-web/SPARK-KITS.HTML I think this might help.

I can never seem to get the pictures to work, even after I "To View Images insertwww. into the URL in the above Address Bar and Go (not refresh)"

Anyone else have this problem?

[Bill75]

I can never seem to get the pictures to work, even after I "To View Images insertwww. into the URL in the above Address Bar and Go (not refresh)"

Anyone else have this problem?

No I never can either. I think he's got some ongoing battle with the software company he paid for that stuff and he refuses to change it. I was able to view things once on someone elses computer a couple of years ago.

[BarryK]

I have some files on my website tech articles page that may help:
http://69.253.166.197/page1/page65/page65.html

about halfway down the page look for two called:
"C3 emissions vac hoses.pdf"
"Dr Rebuild emission diagram.pdf

The first file is the vacuum hose layout from my '78 AIM but even though your car is probably a different year (I didn't check your profile) it should be close enough to let work with.

Regarding the vacuum hose that runs to the vacuum advance cannister it was originally connected to a ported vacuum source on the carb (higher up on the carb body) because of emission requirements but you will get a better runiing car if you connect it instead to a full manifold vacuum source on the carb which would be located down towards the base of the carb (below the throttle plates) such as port #3 in your first picture.
Typical advantages to running the vacuum advance for the distributor off a full manifold vacuum source such as port #3 in your pic rather than a Ported or Timed vacuum source such as port #5 in your pic would be better idle characteristics, better throttle response, motor runs cooler, and better fuel economy.

hope this helps you a little bit.

[Maymyvetteliveforevr]

Thanks BarryK!

[JohnZ]

Here is the electrical connection that went to the carb before

Derrick

There was no electrical connection of any kind to the carb on any '71 Corvette; that connector looks like it's for a '72-up alternator field. Any idea where those two wires go?

[dshanks]

Well, I might be able to help with some of the questions:
Here's a picture of the lines and where they go
Bill

Thanks Bill, appreciate the time you took to get a response back to me.
Im still a bit confused because it looks like we have some differences in our carb. And I dont know enough about it to know what they mean.

[dshanks]

There's are diagrams of the hose connection on Dr. Rebuild's site. Here's a link
http://www.docrebuild.com/dr-r-web/SPARK-KITS.HTML I think this might help.

Hi there, thanks for the link. It doesnt seem to work for me either. Not sure why, maybe a plug-in error or something. Ill check back later, maybe they'd have addressed it...

[dshanks]

There was no electrical connection of any kind to the carb on any '71 Corvette; that connector looks like it's for a '72-up alternator field. Any idea where those two wires go?

Hi John, I dug up this photo of the motor before the restoration. It has this electrical connection in the pic, looks like it has something to do with the spark advance??
Its attached to the carb but might not be a part of it??

[dshanks]

The screws you mentioned on the bottom of the carb are the idle mixture screws, located on each side of the carb. They are adjusted equally for a smooth idle.
Bill

The car already has a smooth idle and drives nice, the problem is that my secondaries aren't engaging at WOT.
Should I just leave these screws alone?

[LVMYVT76]

I don't have a 71 but, doesn't this control the fast idol? When the car is shut off, it drops the idol down so the car won't diesel and puff out the carb?

[JohnZ]

Hi John, I dug up this photo of the motor before the restoration. It has this electrical connection in the pic, looks like it has something to do with the spark advance??
Its attached to the carb but might not be a part of it??

Yup, that's the TCS solenoid - determines whether the distributor vacuum advance gets full manifold vacuum or "ported" vacuum. At normal operating temperature, the distributor only gets manifold vacuum in high gear; if the engine is overheating or at cold-start, it will also get manifold vacuum. Under any other conditions, it gets "ported" vacuum (no vacuum at idle). The sensor that determines the overheat or cold start condition is the one in the passenger side cylinder head.

Most people just bypass the TCS and connect the distributor vacuum advance unit to full manifold vacuum; car runs better, runs cooler, has better throttle response and fuel economy.

[Lucky 3]

I don't want to hijack your post but does anyone have pictures of the carb and vacuum lines for a 1969 390 hp 427 with four speed and air. The engine has a two port fitting on the manifold behind the carb and no power brakes. The solenoids on the carb & manifold are missing. The AIR system is also missing. The assembly manual shows the dist vacuum line coming of of the manifold fitting, not the ported fitting on the carb. We have aquired alot of the parts but don't really know what we are missing. The car was worked on by Bubba and his mother and the wiring and vacuum lines are really messed up. Thanks. Bill