Any Fellow Quadrajet userds out there

ThikStik

My sleep apnea is winning
Joined
Mar 27, 2002
Hey Guys,
Just wanted to pick the brain of any fellow qjet users to try to help diagnose the one on my GTO. I expect 0 responses but anyway here goes. Ive got a six speed 466 cid 71 GTO. The qjet has a transition problem which has cost me a race due to hesitation before 4 bbl comes on. I know about the secondary air flap windup adj. and even about drilling out the orifice on the diaphragm. neither adj. helps. It is not a accel pump issue as a drag race gives no problem but on hiway punch it bogs between gear changes. 2 totally new qjets have given identical problems. I ran without air cleaner and beat a guy who had previously beat me. Just that one change, so i am woundering if it may be my ram air air cleaner. There were only 800 made so if gm had a problem with this it never would have shown up. Wanna fix this because its qjet or die as the mileage is awesome , No holley fuel dumper for me!
 
If you remove the air cleaner and it went away, you're probably to rich with the cleaner on. Try smaller jets and metering rods. You may also want to post this on www.v8buick.com
 
Qjet

I love them Qjets!
we ran a ss/d camaro years ago, fooled w/ them so much I thought I was in love! ha ha
the problem you speak of is all in the secondary air door, it is opening to soon, tighten it up, you shouldn't feel any hesitation when it opens, should just pull harder,and harder, I know, you adjusted it! adjust it again! it's still to loose!
Good luck
cruzn57
 
Real men run Holleys! :D

J/K.
Every Qjet I have had had that problem to varying degrees. Sometimes I actually liked it, since it felt similar to a turbo kicking in when those huge secondaries open up.

I just love the simplicity and adjustability of my Holley
 
The air door spring is the only thing that governs steady state door opening versus airflow since the vacuum pot has fully released at WOT. Set your spring so that WOT feels good and ignore the tip in problem for now. Make sure the air door closes and is not set so loose as to be inconsistent. You don't make more power by loosening it. Once that is set , look at the vacuum pot.

You may have already opened up the orifice and made it open too quickly. On tip in the spring for the door will help alter the initial tip in point but it has no damping, thats the vacuum pots job. The factory items had quite a variation in the opening rate from fully pulled to fully opened. Go to an aquarium store and get one of the those brass air line valves. Open up the orifice on the vacuum pot to make it fast reacting. Insert the valve between the carb vaccum port and the vacuum pot. Now tune your tip in with the valve. You can close the valve to make the secondaries take a minute to open or open it to allow opening in a split second. You want somewhere between those two points. I used to adjust it mostly in the driveway by squeezing the thing shut and letting it open, adjust the valve each time until it looks right then test drive.

The air door springs thermal cycle and relax over the years so there is nothing wrong with the fact that the thing needs adusting. Unlike a Holley though you cannot change the spring stiffness, only the preload.

Set properly, the vacuum pot will not allow the engine to bog. Just make sure you don't confuse the recovery from the secondary bog as more power than an engine that smoothly powers up with the secondaries set correctly. Its easy to be fooled by the "butt" dyno.

Final thing, make sure the vacuum pot linkage can hold the air door fully closed otherwise the air door can crack open initially without the vacuum pot controlling it.
 
Thanks for info guys. Let me give more info since yall seem hard on the trail. It absolutely is a transition only problem as this motor just dynoed 380 at the wheels. (no headers BTW). And it was a tad rich under full power. I pulled air cleaner to reach this best pull which did yield more hp but mixture stayed the same. I swear I thought pulling air cleaner makes an engine run richer-I read that in CC a ways back and yes, remembered it because it sounded backwards to me. Its definately a 2nd air flap prob. no choke lock out problem, no float issue, pulgs read good, no tip in issue, no acc pump prob, and ive tried diff rods/hangers. Two new condition carbs have done same exact thing. this is why im starting to suspect factory ram air AC base. It really hunkers down low in respect to carb's air horn. This design could be causing weird turbulence that is throwing off flaps. And the time the flaps stay closed the longest is when your running along on a hiway race in hi rpms waiting on the "go" if you ever floor it and then let off and then Refloor it-then forget it. The freggin flaps stay shut for 3 whole seconds. Its like they are being sucked closed. And it is not always that bad. I know a tight 2nd flap windup is best. BTW i will try vacuum pot idea.
Oh yea, I run later model quads. They have better castings and have the little apt adjuster which fine tunes the primaries+electric choke.
But , no older qjet I ever tuned has done what these 2 new ones have!

:) .:mad:
Thanks guys
 
Originally posted by rick cain

Get Doug Roe's Quadra jet Book, and start with that.
Then some spare secondary hangers, and once you have the *base* dimension of like a L, you can make a jig and bend up the others, and get it really right.

Lots of tweaks for QJets, just too often people don't go the full 10 yards, or don't know about drilling out the secondary refill orfices, or using a perferated pull over tube, yada yada.

Only way to get a Holley right is updating to the metering blocks that use the weber carb, emulsion tubes, and then starting from scratch.

Either carb takes about the same time to get CORRECT, and it takes ALOT of time to get it CORRECT.
 
Yea Bruce,

I do have the Doug Roe book - God that is the most A.D.D book ive ever seen. He is a terrible writer-his info just skips around from place to place but yes it does have info.
I did drill tubes out on the other qjet, like on the Ford Cobrajet Qjet. May try it on this latest problem carb. Its funny that only the two later model castings are doing this. I have noticed that older carbs have slats in their sec. air flaps. I even tried changing to these style flaps on this carb-no better no worse. Its like the flaps are just staying sucked down because it mostly happens from a high rpm-then stab it wot scenario.
Thanks

ps I need to borrow my friends open element air cleaner
 
Rick, Go over to Classical Pontiac & look for MR Cliff Ruggels he may be able to help you. He lives in PA I think.
He is a top notch carb man.
 
Originally posted by rick cain
Yea Bruce,

I do have the Doug Roe book - God that is the most A.D.D book ive ever seen. He is a terrible writer-his info just skips around from place to place but yes it does have info.
ps I need to borrow my friends open element air cleaner

I did ALOT of playing around with a 19074201, wound up finding there were several sec pull offs that would work, 3 actually, 2 made hardly any change, but the 3rd one was just magic. You never felt the secondaries, tip-in and the motor just answered the helm in an amazing way. Might look around and see what you can find. The carb shop used to offer an idle channel restriction, and idle jet it that also was neat to play with.
 
Fangling with some diff diaphragms? Couldnt hurt. I did drill one to allow vac to bleed off quicker. (drilled inside tube ) No change. I wish the Roe book addressed this. I know the carb shop guys do this. i bet carb shop or Jet techs could nail this problem right away but they want to just rebuild whole crb. The qjet on here now is an EdelCrock and like i said , it is doing identical thing as my other late model qjet.
Any idea Bruce which diap you used and was it on a late model?
Thanks guys
ps Littlesix, is Classical Pontiac a website?
 
I think you want the secondarys to open LATER as the RPM's are too low when they open, which causes a large drop in manifold vacuum. That large vacuum drop results on lack of airflow thru the carb, which in turn results in lack of fuel being picked out of the carb, and your lean bog. If you can delay the secondaries a little, it will most likely help big time. I KNOW thats the deal with vac secondary Holleys. Matter of fact I just did a 600 vac secondary on a Ford truck and the guy swears its a 2bbl. Thats how invisible I got the transition
 
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