Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Dialing in your rebuilt Quadrajet carburetor => Topic started by: F250 Restorer on October 29, 2011, 07:15:09 PM
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I have a newly rebuilt QJ from 78. I kept all the settings, mix, idle, secondaries that it was set at for a sbc. I did change the m. rod piston spring to one with more tension since it is going on a 309 ci ford I6.
I'm hoping someone here would be so kind as to give me a basic step by step guide with this. I've worked on carbs before, but this is by far the most complicated. I'd appreciate any help offered.
Thank you.
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Stronger springs simply start the power piston up earlier when engine vacuum drops off sharply. In most cases, use the strongest spring that will have the power piston down at idle, as it will get it moving up the earilest and quickest when you hit the throttle hard, or any situation where the engine needs more fuel.....Cliff
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I installed the rebuilt today. Although I disconnected the choke, and the idle screw is all the way backed out, I can't get the idle to drop to normal. First off I tried to adjust the mix, and there was no difference whether all the way in or out. So I snipped off a rung of the springs, and now it starts to shutter when all the way in. I assume I should snip off another bit? The engine should die when all the way in, right? Also, I'm guessing it is idling at about 1200 rpm, minimum, and surging. When I try the 'tip in' it speeds up, so I think it is lean?
Normally I would think vacuum leak with the idle staying up. Tomorrow I will spray around the crab with starting fluid, and see if I have a leak.
Help is GREATLY appreciated.
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I also found this and wondered if someone could explain it: Don't try to set the idle without holding the hot idle compensator tang back on the back of the carb.
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I would block the HIC hole and not use it. Just another potential vacuum leak at idle.
The engine should idle down, if not, too much idle bypass air, vacuum leak, secondary throttle plates not seated well in their bores, etc.
The mixture screws may not kill off the engine when seated, as some fuel is delivered thru the exposed portion of the idle transfer slots at idle speed. Turn the screws in till it just slows the engine, back them up about 1/2-3/4 turns, should be pretty close for idle mixture settings.....Cliff
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I finally got around to working on the carb again. I emptied it, turned it over and could only see a line of light around the edge of the primary and secondary butterflies. I was able to idle it down to eight-hundred rpm, took it for a drive, but got back and it was up to 1000 rpm.
I noticed there is a slight ooze of fuel from the booster holes, just getting it wet. I also noticed that when I manually push the throttle closed the idle drops 100 rpm.
Is it normal to have the fuel spray out when I disconnect the fuel line? I've never seen that before.
I should also note that I sprayed around the base with starting fluid to no affect.
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I loosened the s. flaps and played with then to get them positioned correctly.
All four butterflies look seated. Still it idles at 1,000 rpm. I can get it down to 800 rpm by screwing in mix a bit, but then it runs rough. It also surges 100 rpm up and down.
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It's got to be getting idle air from someplace. If all 4 throttle plate are fully seated, the engine should stall out.
Did you eliminate any idle bypass air in the baseplate?
Plugged the vacuum hole leading to the choke housing for the hot-air choke?
Linkage adjusted so the primary throttle plates are fully closed when it's in use?.....Cliff
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It's got to be getting idle air from someplace. If all 4 throttle plate are fully seated, the engine should stall out.
Did you eliminate any idle bypass air in the baseplate? If that wasn't mentioned in the book, then I did not do it. How do I do it?
Plugged the vacuum hole leading to the choke housing for the hot-air choke? I installed the housing from a latter model with elec. choke. The v. hole does not continue through housing.
Linkage adjusted so the primary throttle plates are fully closed when it's in use?.....Cliff yes.
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It's got to be getting idle air from someplace. If all 4 throttle plate are fully seated, the engine should stall out.
Did you eliminate any idle bypass air in the baseplate? If that wasn't mentioned in the book, then I did not do it. How do I do it?
Plugged the vacuum hole leading to the choke housing for the hot-air choke? I installed the housing from a latter model with elec. choke. The v. hole does not continue through housing.
Linkage adjusted so the primary throttle plates are fully closed when it's in use?.....Cliff yes.
by the way, the carb # is: 17058504
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I have the idle bypass in both the main body beside the boosters, and in the airhorn. Should I plug one set of holes?
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I would make sure the vacuum supply hole to the choke housing is blocked in the main casting, even if you switched to an electric choke.
Make sure any idle bypass holes in the baseplate are blocked, no need to block them anywhere else.
Once you get full control of all the air entering the engine, you will have full control of the idle speed of the engine.....Cliff
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Thanks, Cliff. Since I'm sort of new to the QJ, can you please point out which holes to plug, and how to do it.
Thank you.
(http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010570.jpg)
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The two holes closest to the idle mixture screw tips, at 1 oclock and 11 oclock in the pic. Best to tap them and install a small set screw, 8-32 or 10-32, then we can always install a drilled brass set screw later if needed....Cliff
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Cliff: Getting a tap in the right side bore is out of my ability. I suppose I could take it to a machine shop, but at this point I am not willing to do that. What I did was fill the hole with epoxy. If I need to open a hole later for more idle bypass, or the nozzles are dribbling, then I can do that. Right now I will reassemble and see how it does on my ford 300, with 250 hp.
All your help has been exceptionally valuable.
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Cliff--
Haven't installed yet. Did I ruin it by filling the holes with epoxy?
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Wouldn't matter what was used to plug the holes, as long as it stays put.....Cliff
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Runs great, just a little hesitation when the secondaries open. What do you think?
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Secondary transition is fully adjustable using the adjustment spring. Make sure the link from the pull-off is holding the airflaps tightly closed at idle (high vacuum)......Cliff
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Since I filled the idle air bypass holes the idle is good, but it acts like a v.leak, surging on the v.guage and rpm's, mostly at 16 on guage, then up to 17, and quickly drops to 14 for a second, then up to 16 again. (At idle with the Edelbrock on I read 19 on the v.guage.)
I've sprayed around base with s.fluid and there doesn't seem to be leak. I also sealed up choke housing good. I can, and I don't know if this is normal, see fuel dribbling out the p. boosters.
Cliff, do you have any ideas? Thank you.
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Did you adjust the idle mixture screws to give it some more idle fuel. If it has nozzle drip, it's not completely on the idle curcuit. Usually this means it's to lean, or needs some bypass air, or both....Cliff
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I'll try to back out the mix screws past where I normally would, and see it that stops the surging and the nozzle drip.
If that doesn't help, should I remove the restrictions in the bypass air that I got from you? Because with the main bypass holes now plugged, I don't know how to get the carb more air.
Thanks.
I should mention that the only vacuum line I have connected why trying to tune it is the pcv line.
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Are you using vacuum advance? It should be hooked up when tuning....Cliff
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How do I get it more air and make it stop surging? You said when it is pulling fuel from the boosters it is a sign it needs more air and could be lean too.
Should I remove your restrictions I placed in the air bypass?
Should I drill out the idle tube restrictions and/or the mix screw holes?
Thank you.
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(http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010552.jpg)
(http://i659.photobucket.com/albums/uu316/bobbyrogue/P1010553.jpg)
Now that I have plugged the idle bypass air holes in the throttle body, should I remove these restrictions to supply more air?
BTW, I did drill the mix holes slightly.
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Those are main airbleeds, and have nothing to do with idle fuel, or idle air.....Cliff
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From your pictures, it looks like your idle tube is missing, did you remove it?
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You must be referring to the top photo. At the time of the photo they were prob. out. I bought replacements from Cliff, and hopefully they are back in. That would have been a real goof, ah?
CLIFF, besides drilling the mix orifices, what should be the next step to make this idle right w/o the surging?
Thanks.
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Cliff, can you please help me with this carb. I was advised to plug the bypass holes in the t.body completely. Now you state it may need more bypass air and/or be lean. Where do I go from here? Please advise.
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Reading back thru the thread, it appears that you had high idle issues, and couldn't get the engine to idle down. Now you have "nozzle drip"? Sounds like it doesn't have enough idle fuel to the mixture screws for what you are doing.
I'd back the mixture screws out to see if you can get the idle to smooth out. If they have no effect I'd open up the idle tubes, or close down the idle airbleeds, or both. What size are the holes under the mixture screws?.....Cliff
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I haven't run it since I drilled out the mix holes. If backing out the mix screws has no affect on the surging/nozzle drip, should I drill the restrictions in the idle tubes, or just purchase diff. ones from you.
If I should drill, what would be the size of drill to use?
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I wanted to mention that since I plugged the bypass air in the throttle plate I have had to turn the idle screw in quite a bit to get it to idle. That means the primary flaps are open a bit, and, I imagine that is what is causing the nozzle drip and surging.
Where do I go from here? Thanks, Cliff.
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A Happy and healthy Easter to you and yours, Cliff, and to all others on this forum.
I didn't hear from anyone, so I went ahead and read through the modifying section of the book. Since I no longer have by pass air, I guessed that the stage 1 recipe would be too little for my carb. I hope that was correct. I drilled the idle tubes at .045". I wanted to enlarge the down restriction too, but found it to be considerably larger than .045", so I left it. I will try it tomorrow and see how it fares.
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Cliff, what size should I drill the idle tubes at? Where would you start?
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After sinking about $300 into this project, I do not want to give up on this carb. I found a diagram online that really helped me 'see' the idle system and understand how it works. I want to post it here to help anyone else who is struggling.
(http://i659.photobucket.com/albums/uu316/bobbyrogue/carb.jpg)
I spoke to Cliff and he is as perplexed as I am. I'm sure it is b/c of my lacking knowledge of carburetors. But when I install once more I will do the tip in again. If the engine sp increases, it needs more fuel. If I pull a v.line and the engine sp. increases, then the carb needs some by pass air.
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After sinking about $300 into this project, I do not want to give up on this carb. I found a diagram online that really helped me 'see' the idle system and understand how it works. I want to post it here to help anyone else who is struggling.
(http://i659.photobucket.com/albums/uu316/bobbyrogue/carb.jpg)
I spoke to Cliff and he is as perplexed as I am. I'm sure it is b/c of my lacking knowledge of carburetors. But when I install once more I will do the tip in again. If the engine sp increases, it needs more fuel. If I pull a v.line and the engine sp. increases, then the carb needs some by pass air.
My next question is regarding nozzle drip. I found online that a rebuilder says diff. QJ's have the main discharge nozzle protruding into the air stream diff. amounts, and he states the ones protruding more suffer from the drip. He recommends tapping the nozzles deeper into their housings. Could you please respond to this?
Also, regarding the drip: Although my engine is a 300 I6, the head is ported and larger valves have been installed, allowing it to breathe well. It also occurs to me that the runners in my intake are divided top to bottom for a double plane intake. The primary side of the carb gets 1/3 of the runners. With larger valves, the air must be moving at great velocity. Is the greater velocity adding to/creating the drip? Should I therefore use the open base gasket so the full runners are used, thus dropping the velocity of the air, creating less pull?
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I am having difficulty. If I had a customer having problems, I would go out of my way to help them, especially if I were trying to build my business. Don't you think that a simple 'do this, then do this' would be in order? But instead, I am ignored b/c I am lost. How helpful.
The bottom line is this: I can take an engine apart and rebuild it. I have successfully rebuilt several carbs. But, like many mechanics, I get lost with the QJ, hence the nicknames for this carb. After studying your book for more than two weeks, and working for about two weeks on a QJ, and spending about $300 on the rebuild, I can not make sense of it, and, my posts are ignored by Cliff. That is what my article will reflect--the truth. And, that is what I will say on the forums.
When it was time for me to buy something, I got your time. From then on I got a fleeting response on your forum.
I will resolve this on my own. Now I understand why this carb has such a poor reputation.
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I've went over the entire thread several times, and provided some advice over the phone in between.
The diagram provided is not even one of your model carburetor, but a much earlier design with direct upper idle airbleeds. It also shows a "fixed" idle bypass, and off idle port, not a transition slot like your unit uses.
The last time we spoke, I provided two test methods for you to use, to determine a course of action.
Pulling a vacuum hose will mimic adding more idle bypass air. If you have enough idle fuel at the mixture screws, then you can slow the idle down, re-adjust the screws, and get off the main system. All that would be needed at this point, would be to add a little bypass air, leave everything else alone, and start enjoying the vehicle.
A rich idle conditon can be simulated by tipping in the choke flap, or gently placing your hand over the top of the carburetor. If it wants/needs more fuel, it will smooth out nicely at idle speed.
I'm not ignoring anything, just waiting for results from the testing/modifications to see which way you need to go?
I can't crawl thru the computer screen or thru the phone to correct the problems. Like I told you over the phone, if the carb were here, I could get it dialed in less time than it took to type this. I suspect that you don't have enough fuel to the mixture screws, which has the throttle angle too high to sustain idle speed to a point where it's starting to pull the fuel it wants from the main system. No way to confirm this without a few basic tests, as we discussed over the phone, and I haven't seen or heard anything about that since, just a picture of a very early unit on the website, with no questions in either thread.
There is no one in this industry to goes further to help folks out than I do. At least 30 percent of my work load is fixing carburetors and helping folks out who spent money elsewhere. Buy all your parts at NAPA, or from another vendor, and see if they even have a website to answer questions, or even care if you get a good end result or not?......Cliff