72 Carter Quadrajet advice needed

[Dave S.]

I have two questions for which I could use some help.

1. Where is the best place to get a Carb kit for the Carter Quadrajet??? Summit has lots of Holley items but nothing for a Q-Jet.

2. This 72 base motor car has a severe hesitation from idle. Vacuum advance is working and engine pulls 20" of vacuum at idle. Seems to me the carb is in need of a rebuild and that could be causing the problem. Car is a low mileage original and I don't think the carb has ever been touched.

As always any help is much appreciated.

[Joe L.]

Re: 72 Carter Quadrajet advice needed

Dave-----

You can get a "minor" rebuild kit from GM/Delco under GM #17076054. Combining this kit with a new float available under GM #7037705 and you'll have all the parts you need to overhaul a "first run" carburetor.

[Clem Z.]

Re: 72 Carter Quadrajet advice needed

i use hygrade and any auto parts should be able to get it for you. post the number stamped vertically,should be 7042203 or 7042202 with auto trans on the drivers side above the secondary throttle shaft and i will post the correct #s for kit and other parts you need.

[Joe L.]

Correction

I just noticed that the car is a 72 and not a 71. No matter, though. The kit and float are the same. This is a SPECIFIC kit for 71-72 Q-Jets of GM #7041213,7041212, 7042203, and 7042202. It is NOT a "one-size-fits-all" type of kit.

[Clem Z.]

one thing nice about the "fits all kit"

i get enought parts to do other carbs with out buying a new kit. highgrade kits have GM gaskets because some main body to throttle body gaskets have numbers stamped in them and the GM numbers are there.

[Patrick H.]

Re: 72 Carter Quadrajet advice needed

Dave,

I'd agree with Joe's post here and below. The GM kits are nice. I've used them with good success. I use a Jerry Luck gasket, though, between the air horn and main body if I detect any notable warpage. I doubt you will, though. Jerry had gaskets made up at about twice normal thickness and they help seal the air horn if you have any minor fuel leaks.

In addition, is it only off-idle you have a problem?

Keep us posted. I've done enough 71/72 Q-jet carb work to do it virtually blindfolded.

By the way, my 72 is a dog off-idle too. It may just be "the way they were" to a degree. It improves quite a bit when the engine is warm. I always have to be gentle with the throttle, ESPECIALLY when the car is not moving, or it seems to fall over itself.

Patrick

[Clem Z.]

Re: 72 Carter Quadrajet advice needed

just change the power piston lean stop if you do not have to do emission checks.

[Dave S.]

Re: 72 Carter Quadrajet advice needed

Clem,
It,s a 4 speed car, #7042203. For us novices can you explain the power piston lean stop adjustment and how to do it. There is an adjustment screw on the front of the carb w/ a plastic cover on it. It seems the factory didn't want this setting changed. Is that the power piston adjustment???? There is no emissions checks here in Massachusetts, they just tax you to death instead.

[Dave S.]

Re: 72 Carter Quadrajet advice needed

Patrick,
Yes it is only off idle and improves somewhat when warm. I've owned Qjet cars before and this is far to much of a hesitation. Is my engine vacuum situation OK @ 20" ???? I think I'll try a rebuild and go from there. After 31 years I think it needs it anyway.

[Patrick H.]

Re: 72 Carter Quadrajet advice needed

Dave,

The 72 hesitates much more than my 71. Why? I don't know. It's got a rebuild kit in it, and the distributor curve is good. Who knows.

I'd at least try the kit. Can't harm it at all.

Patrick

[Clem Z.]

Re: 72 Carter Quadrajet advice needed

the Q jet uses 2 different types,if the power piston has a steel pin sticking out the bottom the adjustment is in the throttle base plate behind a small expansion plug between the 2 idle/air adjustment needles and if the power piston has a steel pin sticking out horizontally the adjuster is inside the float bowl. you need to raise the power piston in the bore so a smaller part of the tapered metering rods are in the jets. you could also just try 1 step bigger jets but this will richen up the whole fuel curve where raising the metering rods will only richen up the bottom end of the fuel curve.

[Clem Z.]

Re: 72 Carter Quadrajet advice needed

the hygrade #s, kit 579A,choke pull off CPA86 and the float FL1. these are all good parts as i have used them for years on 100s of carbs and they all are as good as orignal GM and a lot cheaper.some kits contain more than one gasket for the same place on the carb,just match up the orignal gasket to the one in the kit and discard the others. clem

[Patrick H.]

Re: 72 Carter Quadrajet advice needed

Clem,

I use a stiffer power piston spring under the power piston. Would you guess this accomplishes the same thing? It did seem to help, but the car still isn't the best off the line.

Of course, when I got the car the previous guy who put in a carb rebuild kit forgot to reinstall the power piston spring AT ALL. Needless to say it runs a lot better than it used to.

Patrick

[Clem Z.]

Re: 72 Carter Quadrajet advice needed

the stiffer power piston spring will help it go richer at a higher engine vacuum(sooner) but raising the metering rods in the jets will cause it to be richer just off idle causing the lean stumble to go away.

[Roberto L.]

Re: Correction

Just to know and learn two related q's. Which is the valid kit for 7040503 (base manual California)? And, where do you get the primary needles (correct numbered) used in the Qjets (or secondarys, the same). Thanks, Roberto, NCRS #30019, RMC