Quadrajet or Aftermarket?

[Bonnewagon]

They have very lean idle ports. So lean that even after uncapping the screws, turning them makes little difference. The trick is to drill out the ports to pre-emissions specs. IIRC I think that was around .095". Then you can tune the idle mixture for a more aggressive cam.

 

[403Olds]

I just hooked my choke up to switched 12V, when I converted mine over. Works fine for a summer car. I typically don't have it out less than 45 degrees anyway.

 

[ELCAM]

Usage of part number 17085226:

It appears it did not come with the front Vacuum Break.

Rear only vacuum brake:

Front vacuum brake Note the slot in the secondary air valve lever, and only a hole in the rear vacuum brake lever.

The rear vacuum brake installed now is from a G body of a similar year it should have two slots. The vacuum brake should look like this:

Also missing this linkage that goes to the secondary valve lever.

 

[TheSaint]

The Qjet in the picture is a truck Qjet with the a grey connector for a 2 stage accel pump. Its not a true CCC Qjet. A real CCC Qjet that would come in a G body would have a blue connector for the air fuel mixture control solenoid and a white plug the the throttle position sensor and a normal accel pump.

I have a dualjet in my 84 Monte that sounds more like the one you’re describing.

 

[Longroof79]

They have very lean idle ports. So lean that even after uncapping the screws, turning them makes little difference. The trick is to drill out the ports to pre-emissions specs. IIRC I think that was around .095". Then you can tune the idle mixture for a more aggressive cam.

Yeah Mark,
I figured it to be a lean running smog tuned carb. I'll probably use it for parts. The carb on my car now is from a 400 small block that seems to run pretty well.
Still has a bit of a off idle flat spot. I find that it still out performs the Holley that I had on there previously.

 

[Bonnewagon]

Jack an off idle flat spot can sometimes be cured by changing the metering rod. Inspect yours and if it is kind of fat at the off idle/mid range section, a thinner profile will give more fuel at that point. This is another reason I swear by Doug Roe's Rochester book. He shows you the profile of a metering rod and what part of it affects the power curve. He also lists primary and secondary metering rods by part number and specifications. What year is your carb? The Chevy 400 was early 70's right? The later carbs that had the APT feature [Adjustable Part Throttle] you are able to turn the rod hanger adjustment and move the metering rod up or down in the jet itself. That affects your off idle more than anything by getting the rod tip out of the jet faster. There is a plug in the top of the air horn. It pops out and you can stick a double D socket in there to adjust it. I used to use the ground flat end of a secondary metering rod hanger to do that adjustment.

 

[Longroof79]

Jack an off idle flat spot can sometimes be cured by changing the metering rod. Inspect yours and if it is kind of fat at the off idle/mid range section, a thinner profile will give more fuel at that point. This is another reason I swear by Doug Roe's Rochester book. He shows you the profile of a metering rod and what part of it affects the power curve. He also lists primary and secondary metering rods by part number and specifications. What year is your carb? The Chevy 400 was early 70's right? The later carbs that had the APT feature [Adjustable Part Throttle] you are able to turn the rod hanger adjustment and move the metering rod up or down in the jet itself. That affects your off idle more than anything by getting the rod tip out of the jet faster. There is a plug in the top of the air horn. It pops out and you can stick a double D socket in there to adjust it. I used to use the ground flat end of a secondary metering rod hanger to do that adjustment.

Thanks for all your advice, Mark. I do have the Doug Roe Rochester book. I guess it's time to refer back to it again. Very informative, and a lot of good info in there.
I'd have to check back on the carb serial #, I believe it might be a '73-'74 carb. I must have it written down somewhere. I usually like to keep a record of what's what. If I haven't displaced it that is.

 

[Bonnewagon]

Jack the problem with the pre-1975 carbs is that the metering rods are a little longer than the post 1975 ones. They are not interchangeable. Even with eight years of production, they are much harder to find than the six years of the later ones. Seems odd but that is what I have found to be true. That said, I like to use the later Q-jets simply for the APT, and the electric chokes. The electric choke can be back fitted easily on the hot air choke models. But the old intake manifold choke stove coil type are totally impossible to convert. I have tried and failed. It's funny now, but I used to trip over Q-jets at swap meets years ago. The lowest I paid was three dollars for one. So I stripped them down for parts and I have a large selection of rods and jets to play with. You can get jet sets on Fleabay easily, but metering rods are tough to find and expensive.

 

[TheSaint]

Oil pressure switch as stated is best way.

First fix your fuel line. It is kinked and won't flow as is.

Second it is the wrong carb. You need a non C3 ECM carb which is pre 1981.

Could you point me in the direction of that carb?

 

[78Delta88]

This would be a close idea.

Basic carb, this one has electric choke, and hook up for auto transmission.

It will need special tool for idle metering adjustment.

I can't vouch for supplier, haven't used their service. I usually pull my cores from project cars, swap meet, sometimes eBay. I rebuild my own, and use vintage oem as much as possible.