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Old 09-10-2010, 08:05 AM
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quadrajet electric choke

hello all, i recently installed a quadrajet onto my350 chevy , it wasnt brand new out of the box , but in very good condition, it has an electric choke on it which is wired in the problem im having is when i start it up it runs up like normal but after it has warmed up like 15/20 minutes it still idles in park at like 1200 1300 rpm, the idle screw is backed right out, what do i adjust the electric choke?, also i notice when i rev it up by hand that the secondary flaps do not tip open it does rev up well ,but should they open, i did notice the rod ledding from the flaps to the choke seem stiff, but im not sure if they are supposed tio be like that , what do i do ,,,,,,,,,,,,,,,,,,,,,,,sorry if there is not enough info,,,,,,,,,,,,need help

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Old 09-10-2010, 09:01 AM
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With the choke closed the fast idle screw should allow for a fast idle. But once the choke opens, the idle speed should be controlled by the curb idle screw- like you'd normally use to adjust the idle speed.

So, providing the choke is completely open, the choke's fast idle screw needs to be adjusted CCW to lower the fast idle speed.

What you can look for, is the throttle linkage not being in contact with the curb idle screw, even though the choke is open all the way. If that IS the case, it will be the fast idle cam either hanging up, or the fast idle screw adjusted too far in (CW).

Other things that can cause the idle speed to be too high is a vacuum leak or too much ignition advance. After you sort out the idle speed, you can go back and (using a vacuum gage, preferably) readjust the idle air/fuel mixture screws for the best idle vacuum and most idle speed. If the adjustment of the mixture screws causes the idle speed to become too high, use the curb idle screw to bring it back to where it's supposed to be.

Here's some links that may help you:

Q-jet rebuild w/photos- HERE.

Q-jet exploded view- HERE

Q-jet carb adjustments (including fast idle)- HERE.
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Old 09-10-2010, 09:58 AM
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The secondary flaps aren`t supposed to open with the car sitting in park, they are designed to open under load. If they open with just revving it in park could indicate the secondary flaps are too loose.
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Old 09-10-2010, 12:58 PM
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Quote:
Originally Posted by badmystur
hello all, i recently installed a quadrajet onto my350 chevy , it wasnt brand new out of the box , but in very good condition, it has an electric choke on it which is wired in the problem im having is when i start it up it runs up like normal but after it has warmed up like 15/20 minutes it still idles in park at like 1200 1300 rpm, the idle screw is backed right out, what do i adjust the electric choke?, also i notice when i rev it up by hand that the secondary flaps do not tip open it does rev up well ,but should they open, i did notice the rod ledding from the flaps to the choke seem stiff, but im not sure if they are supposed tio be like that , what do i do ,,,,,,,,,,,,,,,,,,,,,,,sorry if there is not enough info,,,,,,,,,,,,need help
You might want to get a better understanding of how the Qjet works. First of all, there is no linkage from the choke to the secondary "flaps" (actually, they are called air valves). The rod you are probably talking about is the vacuum pull-off, which is not related to the choke. The choke coil only controls the choke plate above the primary side of the carb. Are you sure the choke has power once the engine is running? Does the choke plate on the primary side open fully when the engine is warm? You adjust the electric choke the same way you adjust the hot air choke on a Qjet - you loosen the three retainer screws and rotate the black plastic choke coil one way or the other to change the choke opening point.
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Old 09-12-2010, 05:35 PM
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quadrajet

hello, hey thanks cobalt i useed the instructions and it went well, also hey thanks joe yeh i didnt have the right wording what i should have said was the lingkage that was seemed to be sticking was on the outside of the carb at the rear coming from the secondary shaft it was a linkage rod that leads upto where the throttle cable hooks onto was sticking up after cleaning and some lube it seems to be ok ,,,,,,,, but i do still have a slight problem with the carb , that i need help with under full throttle say from pulling away from a stop it seems to be bogging just a little at high rpms, i have set the timing, set the air screws using a vacuum guage,,,,,,it does have the electric choke hook up , works great when starts up runs up fast the idles down like it should ,it idles great nice and smooth, when your cruisin around say mid throttle its fine too, is this a problem with the seconadry flaps not set just right ??,,,,much appreciated people any help would be greatfull,,,,,,,,,,,,,,
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Old 09-12-2010, 07:38 PM
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Quote:
Originally Posted by badmystur
under full throttle say from pulling away from a stop it seems to be bogging just a little at high rpms... *SNIP* ...is this a problem with the seconadry flaps not set just right?
Try to be a little more clear on the RPM at which you get the bog. Is it w/a LOT of throttle, from a stop- like taking off hard, or is it more after you are under way and then the engine bogs?

If it early- like right at the hit of the throttle that you get a bog, then the engine clears up and accelerates normally, it would be related to the accelerator pump.

If it's more of a bog that doesn't occur at the initial hit of the throttle, it could be the secondaries opening too early.
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Old 09-12-2010, 07:57 PM
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qaudrajet

hey cobalt, sorry about that its at wot, when it bogs seems to do it a few times in a row, but never really clears up, its fine when just pulling away from a light, wa s looking on other sites as well some said it may be flaot adjustment as well , but would that not affect the whole range from low rpm upto wot???, thanks again cobalt i appreciate it ,,,,,,,
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Old 09-13-2010, 06:25 AM
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There's a good chance the secondary air valve is opening prematurely. If that happens, it causes the engine to bog because w/only a "passive" secondary enrichening circuit, there's not enough fuel to cover the "hole" created by the too-early opening of the AV. This is what the secondary accelerator pump does on a double pumper Holley.

So when the engine bogs, the AV closes until the engine is pulling hard enough to open the AV again- then another bog, et cetera. It will continue to do this until the engine is spun up high enough to run cleanly w/the secondary AV fully open.

But on many engines- when properly adjusted- the AV never fully opens. The Q-jet flows 750/800 CFM and unless an engine is pretty bad-A or turning high RPM, it just doesn't need that much flow, so the AV never fully opens. However, if the AV is adjusted so the spring pressure is too light, it can open too much, too soon.

The AV shouldn't open when you jazz the throttle in Park. Only when under a load, and at sufficient RPM will you want the AV to open. Also, there shouldn't be a noticeable transition into the secondaries. Many guys think the carb should "bang" into the secondaries, but what's happening is a bog when the secondaries open, followed by the engine 'catching up' to the carb- this gives the impression of acceleration. A timing slip will show otherwise.

There is an adjustment for the AV spring. You can get a 'feel' for how it's adjusted by pushing the AV open (engine OFF) w/a finger. It should shut w/o hesitation when you let off pressure. After you've been working w/the Q-jet for a while, you will get a feel for how the AV is dadjusted just by doing this.

So in your case, start by adjusting the AV 1/2 turn CW to cause the AV to open later (more spring tension), then road test. BE SAFE!

From HERE:



BEFORE you loosen the lock screw (the lock screw is the allen head screw shown in photo above, right at the end of the short leg of the allen wrench), note the position of the spring's adjuster (seen looking at the side of the carb in PHOTO below)- it has a straight blade screwdriver slot in it- that way you have a baseline from which to work from if you get "lost" during the process.


It's worth noting that there are other causes of bogging. The AV is one that is often encountered- but not the ONLY cause, by any means. So, if you still have issues after trying the air valve adjustment, get back to the forum and well see what else can be done. Do one change at a time.

Good luck.
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