So my quadrajet works fine, until i hit the secondarys. The ( what i believe to be the choke butterfly ) isnt hooked up to any thing, and tied wide open. The secondarys wont pull fuel at all, and it dies at wide open. I was told that the top butterfly isnt the choke, but an air dam? I have everything, but i have no clue else wise. Any experts on the topic? And i know, its a terrible carb, what with the quadrapuke, quadra toilet, ect. It was never run on a car after a rebuild, and was $25.
nothing wrong with a quadrajet, very simple, you have a choke and you have secondary flaps(the two almost round spring loaded flaps) so you have the choke wired open? can you take a pic of your carb?
Actually a good carb if built right, thay will make power and get decent mileage at cruise, but they need to be right.. Look at the secondary air valve and make sure the hangars are hooked to the metering rods
red circle is the choke, blue circle is the secondary flaps, the secondary flaps are spring loaded and remain closed untill vacuum from the engine pulls them open.
there is no choke, so its not causing you any trouble, when you tap the secondary flaps do they have much resistance? or do they kinda fall open, they should right snap shut.
The first thing I see wrong is that you are missing the link from the choke pull off to the secondary air valve, which is the flap you have open in the second photo. This is needed as it keeps the flap from opening too soon. Once you fix that including making sure the choke pull off works. check and see that the secondary hanger rises when you open the secondary air valve. This is the part that is between the two butterflies. There are two metering rods that are attached to the secondary hanger and are what control the fuel delivery to the secondaries. So make sure that they are attached to the secondary hanger. HTH
On the pass. side of the carb is a lockout device that releases only when the choke is wide open - make sure it's allowing the butterflies to open. Q-Jets can be a mess when cobbled, completely reliable, trouble free & economical when done right. Keeping the fuel pressure below 5 lbs. is a must.
so when you use your finger to poke where i have placed the red dot does the flap snap shut, i mean give it a good fast jab, if not the the tention is set to loose and your car will bog.
so with your car running, hood up, air clearner off, can you operate the carb by hand? rev it up to about 2000 and then wide open for a couple seconds, what do the flaps do?, do they open a little or do they go wide open?, dont stand near the fan when your doing this.
Well, im not running a fan for that reason, iv seen em brake loose. I havent had a chance to do it with the flaps shut yet. I always ran it with a piece of bailing wire holding them wide open, and it wouldnt run on the secondarys.
now were getting somewhere, the flaps have work on there own, if the tension is set correctly they they will only open as wide as the engine requires. your carb may be 625 cfm, but if your engine is only capable of useing 500cfm then the idea behind the flaps is they will only open enough to alow 500 cfm in.
those are actually an air AND fuel metering valve. you have them wide open, you will be full rich as soon as the secondary butterflys open. that carb you have is 750 CFM and the reason that it can work on everything from a 230 to 500 inch engine is because of that. the sec air valve has a small plastic cam in the center that the secondary hangar rides on adn as the enging demands more air and opens that valve, it raises the rods out of the .120 hole that they sit in and gives fuel accordingly. if the tension is off, the rod depth is wrong or that cam flattened then it will cause you major headaches. i love these carbs and specialize in them in my carburetor business. i got 14mpg around town in a 10.7:1 compression 461 olds making about 450hp in a 4000lb car with one of those.
heres some good reading on q-jets http://209.85.173.132/search?q=cach...t+power+valve+spring&hl=en&ct=clnk&cd=9&gl=ca
That really puts into perspective HOW MUCH BETTER THEY ARE THAN HOLLYS hahaha Its a self adjusting, self tuning carb basically.
Fastest naturally aspirated street car I ever saw was a Buick Skylark with one big Q-jet. They are fantastic when tuned properly, but compared to a Holley or AFB, they are harder for most to understand. Spend time to learn how to use one and you'll never look at anything else.
yes the quadrajet was used on V6,s and V8,s all the way up to the bigblock performance engines [some were 800cfm]' they can be tuned to be as smooth as fuel injection if done right. So they are excellent carbs, when tuned right.
I happen to like Q-Jets. I used to rebuild them myself and it was truly a crap shoot for it to work out 100%. I'm fortunate to have a good local carb shop (Allstate Carburetors in Islip, NY) that does a primo job on them. Once I get them back, I slap it back on, plug and play all the way. The biggest problem I see with them is people not keeping up with the fuel filters which should be changed religiously. Bob Bob
Here's a picture of a Quadrajet similar to yours. The rod you are missing is outlined in red. It is possible get the secondaries working without this. However you then need to adjust the tension on the secondary flap so tight that you stand a pretty good chance of breaking the spring that closes it. HTH
Cliff Ruggles is a noted Quadrajet builder and wrote a very informative book. http://www.cliffshighperformance.com/ Good for any automotive library.
Another note on tuning I haven't seen yet. The dashpot that controls the missing link has a calibrated orifice in the airline. That is what should control how fast the flap opens. Once you have it working sorta right, get a plastic dashpot & drill out that orifice. Then go to a pet store, and get a valve for the air line on a fish tank (It's just a needle valve). Put it in the air line going to the dashpot, and you have can fine tune it for your car & track conditions.. too much power & wheelspin? close the valve a little.
What? The Quadrajet is the most sophisticated carburetor ever produced. Not to mention the most modern carb example you will find before fuel injection was implemented. Those who discount the Q-jet are ignorant of the fundamentals of carburetion, and should be paid no heed. ...by the way guys it's called the secondary air valve, not "flap"
Check out any NHRA/ IHRA stock/ super stock cars and you will see them running in the 10's. We run a Q-jet on our NHRA stock Nova and I have modified the secondaries to open at a quicker angle and some legal internal mods and our 350 runs in the low 12's. These carbs can be made to preform with the best of them and for a lot less cost, good day, Henry.
Dont call it a quadrapuke. they are a great carb. I have overhauled at least several hundred. Used to do 2 a week for a marine engine shop nearby, sometimes more. They work very very well and make great power. In fact they were on a lot of carbed Mopars in the eighties even. The Marine ones are really good. A real performance carb. No unecessary stuff. The advice you have so far from the other carb guy is spot on. Listen to him. Dont let anyone sidetrack you. He knows what he is talking about. Because his advice is so correct i will add nothing.
theres an adjusting screw under the power piston, when would you need to adjust this? there must be a time or it would not be there.
once they are tuned right they will hold there tune for a long time. I have one ive been running for about 15 years!
. Have you had the top off?? Are the secondary air bleed OR fuel tubes installed, they like to fall out and lay hidden in the carb middle assembly, I always give them a wack with a hammer while rebuilding them along with all the leaking lead plugs...H
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