[smuryof]

Hi Folks,

If I want to check if my secondaries are operating properly, can't I do this while the engine is idling, by turning the secondary throttle plate instead of the primaries? Should I get smooth throttle with just the secondaries?

Right now the primaries seem to work fiine, but the secondaries choke and sputter if I hold 'em open, say, 1/4 or 1/2 way or so (independent of the primaries.)

Seems to me the fuel mixture should be the same on the secondaries, so I should be able to move either of them and get a smooth throttle.

If I'm on the road and I open 'em up, the car hesitates pretty bad. If I'm at high RPM it seems to work fine.

I'm not sure, but the secondaries shouldn't kill the engine like that, should they? Or am I just supposed to be careful when I open them up.

??

Thanks
-Jim

[george kujanski]

Playing with the secondaries at idle proves nothing.

The first thing to check is that the air valve spring is not too loose, i.e. permitting the secondaries to open too soon, causing a bog. Also there is a link from the choke dashpot that keeps the air valve closed unless the manifolod vacuum is low, such as during WOT. That also needs to be operating properly.

I suggest you get Cliff Ruggles' book on Quadrajet carburetors. It's around $20, you can get it on Amazon. If you will be messing with the QJ, it'll tell you everything you need to know.

George

[smuryof]

I did order the book so I'll read up on this later. But I'm impatient, so here's more questions if anyone can tell me I'm on the right track. If not, I can always just wait for the book, should be here in a week or two.

Is the dashpot the plunger-like device on the passenger's side of the carb? has a rod hooked to a lever on the side of the air valve?

Is the screw next to the baseplate (under that plunger assembly) the air valve control screw? I tighten it to increase spring tension on the air valve, right?

[Jeff Walker]

Is the dashpot the plunger-like device on the passenger's side of the carb? has a rod hooked to a lever on the side of the air valve?
Yes it is. I also called the choke pulloff. To check it, apply vacuum to it to make sure it works.

Is the screw next to the baseplate (under that plunger assembly) the air valve control screw? I tighten it to increase spring tension on the air valve, right?
The air valve screw is on the RH side of the air horn. There is a small allen set screw that comes from the bottom that you loosen and then adjust the air valve screw to where you want and then tighten the allen screw.

HTH

[Kenth]

To test the opening rate of the sec. airvalves, drive at 40m/h in second gear and put the pedal to the floor, if you car falls on it´s face at first and then pick-up speed, the airvalves are opening too fast and the preload spring needs too be tighten some, adjust 1/8 turn until the hesitation is gone.
You may start at 1/2 turn preload and see what needs to be done, if you do this test and your car picks up speed slowly but without hesitation or stumble you may loosen the preload some until the hesitation returns, then tighten 1/8 turn and you should be fine.
When you´re finished sorting this out and the car picks up speed, but feels somewhat "jerky" you may try richer/thinner rods or a "higher" hanger.
A reference would be CE rods with a G-K hanger.
Short power tips are used with B-G hangers.
Medium power tips are used with G-M hangers.
Long power tips are used with M-V hangers.
Remember though, this isn´t written in stone, only as a guideline.
This should get you started.....

[smuryof]

I've tried that, roughly 40-mph thing, and it loses RPM quickly & then proceeds to stumble, revving up for a sec here and there.

I will turn the adjustment in 1/2 turn and see what happens. If I can find that screw.

[Jeff Walker]

Originally Posted by smuryof

I will turn the adjustment in 1/2 turn and see what happens. If I can find that screw.

Here's a picture for you. The screw head you see is the allen screw that locks the adjustment. The flat tip screw by the air valve lever is the one you adjust. HTH

[71Formula]

Smurof, The screw is on the highest bracket on the passenger side of the carb. Hold the top screw with a screw driver then loosen the allen screw 1/4 turn or so, this will free up the top screw (if you let go of the screw the spring will unwind). Adjust the top screw as needed then tighten the allen while holding the top screw in place. If it unwinds on you (like it did me the first time) reset the spring tension by tightening the top screw until you feel the slack in the spring gone, then tighten 1/2 turn. 1/2 turn is a good starting point but you may need to adjust it some from there.

[smuryof]

I found this and messed around with it for awhile last night. 3 test runs, one with the screw in 1/4, another with it in 1/2 more, then on the 3rd one it slipped out on me so I brought it all the way in and took it out only 1/4 turn - same condition in each case. On the last run, it sounded like half the engine was running - a hard PUp PUp PUp - when those secondaries opened. All the while, primaries remain smooth - so I'm pretty sure at this point one side of the secondaries is clogged or otherwise defective. Intermittently so.

I have two quads, what I'll do is leave this one on for driveability, and rebuild the other once I get Cliff's book.. what burns me is I paid $200 for the quad that's on there now, from a renowned old-school mom & pop carb shop. I wanted to have faith in it.

Thanks for your input folks.

-Jim

[67cruiser]

smuryof, are your sec. flaps opening up the right amount of 1.280?? Hows your sec. cam for your metering rods?? worn out?? ive seen 4 recantly and guys can,t figure out whats wrong with there carbs. I would make sure your sec. fuel wells are not plugged and make sure they are at least .030 hole.

[smuryof]

I hesitate to open up this carb because it was "Rebuilt by Holley" and I would void the warranty or whatever. I plan on fixing the quad I already have and returning this one.

The quad I already had (supposedly rebuilt by CarbKing, not sure if this is true, bought it from another PY member (not CarbKing) who claimed it was) the secondaries work great when I open it up, but the primaries are in bad shape. Way lean. I cracked it open tonight and took a look at the float level, we're at 9/32. The Motor manual specs 13/32 - is that wrong? I wouldn't think 9/32 would cause a lean condition anyway.

The bowl looks crystal clean, so do the jets and metering rods. At this point I think I need to learn how to tell which jets and rods I should be using, and how to identify the ones I currently have to see if they are just too small.

Right?

[David Jones]

There are usually numbers on both the jets and primary rods.

[smuryof]

And then there's the power piston spring, too - right? Wouldn't too light / weak a spring cause a lean condition? It looks / feels like an old spring. I'm gonna grab an overhaul kit, hopefully will have a good spring I can compare against. I don't want to dip this carb, too clean to waste the time on. It's gotta be a jet size or power piston spring issue. Unless I'm missing something else that can contribute to a lean primary throttle issue. Not float, not temp (engine is heating up fine.)

I'll check the jet & rod #'s tomorrow. I'm taking my time, hoping Cliff's book arrives sooner than I expect.

[77 Canamman]

Originally Posted by smuryof

I hesitate to open up this carb because it was "Rebuilt by Holley" and I would void the warranty or whatever. I plan on fixing the quad I already have and returning this one.

There is your problem. This carburetor has been "molested by Holley", and is junk now. All of the jetting, air bleeds, needle/seat assembly have been messed with and replaced with "one fits all" junk. Get rid of it and start with a virgin example. Those rebuilds have given the Q-Jet a horrible reputation.....

[smuryof]

Yeah, when I ordered the unit they didn't tell me it was being rebuilt by Holley. I thought these guys had a specialist working in-house, I should have asked before ordering it. But once I had it sitting in front of me, I didn't want to just go back to square 1, so I thought I'd give it a try, against my trepidation looking at the neon red "Rebuilt by Holley" tag. Too bad, these guys have been a great shop for everything I've needed up until this point. Hopefully they won't give me any flack for returning it. I'd hate to have to stop going there.

[71Formula]

Smuryof, what is the carb that you want to run that is running lean? Post the # here and I'm sure someone can tell you what Primary rods and jets to start with. A lean condition is usually corrected with primary rods and jets...

[smuryof]

That'd be great. 7042264. From what I can tell, automatic / 1972 / Pontiac application. (Non-california.)

[Cliff R]

Unfortunately, the "remanufactured" q-jets from Holley are among the worst. I would imagine that Holley sub-contracts the work out to another vendor. I haven't seen a single Holley remanned unit that was even close on calibration. At least 19 out of 20 of them will have smashed secondary fuel nozzles in the airhorn, they don't even take the time to remove them before they get "tumbled" in the cleaning media. I also believe that they acid dip the castings, as nearly all of the threads in the carburetor will act like their about ready to strip out when you tighten the fasteners.

None of the other remanufacturing companies are really any better these days. We don't even want to see any more of these carbs sent here for rebuilding. Way less labor intensive to start out with a slam worn out "virgin" unit, with a better end result......Cliff

[smuryof]

Right - I plan on returning that unit.

The 7042264 I'm working with (the one not rebuilt by Holley) has 74/47 rods & jets, which I think is stock, right? Shouldn't these be good enough? I don't know how to check the quality of the power piston spring. It "looks" old, for what that is worth.

So, I guess I'll get a replacement spring, maybe get the rebuild kit if that's what I need to do to get a hold of one. What else could contribute to a lean primary throttle condition, besides the float, rods/jets (if the stockers should be fine, which I would think they would be?) and this spring?

A weak spring would cause a lean condition, right?

<Edit> I'll also blow out the primary circuit with compressed air to make sure it's not as simple as a piece of crud in there..</edit>

[Kenth]

#7042264, pri. jets 74, pri. rods 47, sec. rods stamped CR #7045923, airvalve spring preload 5/8 turns, power piston spring #7037305, application CALIF. AUTO. TRANS. 400.

Clean it out good and try as is. Correct areas needed after test, and "tip-in" procedure.