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Author Topic: How to rebuild a Quadrajet  (Read 23042 times)

pozarcar

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How to rebuild a Quadrajet
« on: January 23, 2013, 11:38:16 AM »
I think I posted this up a few years ago, but another post I was reading reminded me of it.  I did a detailed step-by-step post on rebuilding a Quadrajet on the Bandit Trans Am Club forum several years ago, but maybe it can be useful for folks here.

http://bandittransamclub.com/smf/index.php?topic=276.0
« Last Edit: January 23, 2013, 03:04:48 PM by Maryland Bandit »
1978 Y-82 SE 4-speed (1 of 489)
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Maryland Bandit

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Re: How to rebuild a Quadrajet
« Reply #1 on: January 23, 2013, 03:05:12 PM »
Made it a sticky, great write up!

nwrclint2000

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Re: How to rebuild a Quadrajet
« Reply #2 on: January 23, 2013, 03:36:37 PM »
Thanks for sharing! Just rebuilt mine. How do I adjust the mixture screws?
My name is Clint and I'm a recovering addict. I used to be addicted to Japanese food. That is all.

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Maryland Bandit

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Re: How to rebuild a Quadrajet
« Reply #3 on: January 24, 2013, 08:25:31 AM »
To adjust idle mixture screws:
1. Start car and let warm up, choke fully open and idle at curb idle, 650-800 rpms.
2. Turn one side all the way in closed, the other out 2 turns from closed.
3. Hook up a vacuum gage and record the current reading.
4. SLOWLY turn out the screw that's 2 turn out, a little at a time, watch the gage, the vacuum SHOULD start to climb as well as the idle speed. The motor should smooth out as the vacuum climbs. When you reach max vacuum and the gage starts to DECLINE, turn the screw back to where max vacuum was recorded. Count your turns out.
5. Set the other closed screw out the same amount of turns as the one you just did.
6. Re adjust the curb idle since it will have gone higher during the screw setting. Carb is now balanced for optimum lean rich setting.   

pozarcar

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Re: How to rebuild a Quadrajet
« Reply #4 on: January 26, 2013, 11:33:53 AM »
Tom - Thanks for making it a sticky.  Hope it helps folks.  If I can do it anybody can.  When I get home this summer maybe I can come by with my T/A and get your help tuning in my carb.  I think it still idles a bit too high.
1978 Y-82 SE 4-speed (1 of 489)
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Maryland Bandit

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Re: How to rebuild a Quadrajet
« Reply #5 on: January 30, 2013, 07:43:14 AM »
Now that I have a garage, bring it over, I'd be happy to take a look at it.

TA6.6Liter

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Re: How to rebuild a Quadrajet
« Reply #6 on: May 09, 2013, 05:45:26 PM »
Thanks for the posting Pozarcar.  I'm planning to rebuild my Q-jet, so this was a nice peek at what I have in store.  Mine is not in nearly as rough shape as yours, fortunately.

custom

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Re: How to rebuild a Quadrajet
« Reply #7 on: October 03, 2013, 07:44:43 AM »
I had my q/jet rebuilt and used cliff's parts ,The 350 pont runs grood but has a bit of hesitation yet after several attempts to adj.APT ,IMS .Timing . I ended up screwing the APT all the way in and backed it out 2.5 turns to start over as the rebuilder suggested. When I tuned it in I'm sure it was only about 2 turns out at most ,and this was after I'd turned it out 1 with previous adj. So I'm thinking I have to reconsider all the other adj. I have a mild cam kit in it also 2157 E/B cam kit!

Blondylab

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Re: How to rebuild a Quadrajet
« Reply #8 on: May 10, 2014, 03:31:11 PM »
I'm in the process of rebuilding my Q-Jet # 17057266 over on my Project page and was wondering if anybody has ever found a paint to match the greenish color of the accelerator pump lever and the other linkage rods, etc. on the Q-jet ?


jjr

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Re: How to rebuild a Quadrajet
« Reply #9 on: May 10, 2014, 06:58:32 PM »

 The original stuff had teflon in it and isn't made any longer.

 And while you might find a match, it probably won't stay on
very long.

 I don't know if anyone's tried powder coat, but usually we just
plate 'em.

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
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Blondylab

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Re: How to rebuild a Quadrajet
« Reply #10 on: May 11, 2014, 01:26:44 PM »
Do you plate them the same color ?

jjr

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Re: How to rebuild a Quadrajet
« Reply #11 on: May 11, 2014, 10:15:19 PM »

 Yea, I wasn't clear about that exactly. But no, you cannot plate on the
green color, at least not I know of...

 Joe
1979 10th Aniv 400/4spd
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1980 Indy Turbo Pace 301T
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Blondylab

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Re: How to rebuild a Quadrajet
« Reply #12 on: May 12, 2014, 05:34:09 PM »
So, if I wanted to restore my carb back to original factory finish, how would I get the correct color levers, rods, etc. or am I missing something here ?

jjr

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Re: How to rebuild a Quadrajet
« Reply #13 on: May 12, 2014, 09:54:26 PM »

 On Cliff Ruggles forum, someone asked about the green as well, and
there is actually a company that can put the green teflon back on.

 Cliff had told me a while back that the best thing to do was plate them.

 The bodies get chromated and other parts are plated.

 Joe
1979 10th Aniv 400/4spd
1980 Black SE 301NA
1980 Indy Turbo Pace 301T
1981 Turbo 301T
1981 Black SE 301T
1981 Daytona Pace 301T
www.301garage.com/forum/

Blondylab

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Re: How to rebuild a Quadrajet
« Reply #14 on: May 13, 2014, 12:26:08 PM »
Ya, that was me that posted over on Cliff's site. I just find it strange that you can buy chemical resistant carb paint, but not in this color !

Re: How to rebuild a Quadrajet
« Reply #14 on: May 13, 2014, 12:26:08 PM »


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TA6.6Liter

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Re: How to rebuild a Quadrajet
« Reply #15 on: May 13, 2014, 06:40:52 PM »
So, if I wanted to restore my carb back to original factory finish, how would I get the correct color levers, rods, etc. or am I missing something here ?

I used Eastwood Carb Restore II for the carb body to give the chromate color.  Guys who have done Q-jets for years, including Cliff suggested it is close to the original look.  The original plating chemicals are no longer available or legal under EPA laws, due to the toxicity of the chromate.  I've heard you can buy the chemicals, but no way to easily dispose of it once used, or it is very expensive to do so.

Maryland Bandit

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Re: How to rebuild a Quadrajet
« Reply #16 on: May 14, 2014, 06:47:34 AM »
I use the Eastwood carb restore paint also on the airhorn and main body. You MUST make sure those two pieces are ABSOLUTLY grease free every where. Otherwise, the paint will flake off after it dries. Also helps to warm the two pieces up first before spraying. I let them sit in the sun a few minutes first, or in wintertime, hit them with a heat gun before spraying them. Paint sticks better to the warm surface.

1979TtopDeleteSE

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Re: How to rebuild a Quadrajet
« Reply #17 on: October 16, 2014, 09:31:40 PM »
Cliff Ruggles will restore to original for $500 and an 8 month wait.

jvmagic

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Re: How to rebuild a Quadrajet
« Reply #18 on: October 13, 2015, 03:32:20 PM »
Is cleaning the carb crucial in the rebuilding process?  A shop charges around $50 to clean (ultrasonic) a disassembled carb (not sure how disassembled they need it).

Is this worth the cost?

Thanks in advance.

pozarcar

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Re: How to rebuild a Quadrajet
« Reply #19 on: October 13, 2015, 06:33:56 PM »
I just cleaned my parts myself.  Some carb cleaner and some scrubbing should be sufficient.  Want to make sure all the little holes and passages are clear.  You can soak the carb body in some carb cleaner for a while.
1978 Y-82 SE 4-speed (1 of 489)
2010 Plum Crazy Challenger SRT-8

sergon11

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Re: How to rebuild a Quadrajet
« Reply #20 on: March 20, 2016, 08:50:18 PM »
Does any one know how to adjust the quadrajet 4 barrel my was just rebuild and i dont think it was adjusted right and dont want to take it off again and adjust it again can u guy help me out how to adjust it or is it to complicated??

Tyler

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Re: How to rebuild a Quadrajet
« Reply #21 on: March 21, 2016, 08:44:36 AM »

Blondylab ,if you move the rod into the other hole the accelerator pump will give a longer shot of fuel.
Speed limits are for everyone else!

firebirdparts

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Re: How to rebuild a Quadrajet
« Reply #22 on: March 21, 2016, 12:30:25 PM »
Does any one know how to adjust the quadrajet 4 barrel my was just rebuild and i dont think it was adjusted right and dont want to take it off again and adjust it again can u guy help me out how to adjust it or is it to complicated??

It's complicated, but that is part of the fun. 

In the late 70's, they did not intend for folks to adjust the internal part throttle mixture screw nor the idle mixture, and these screws were capped so that you couldn't get to them.  For people like us, though, we remove the caps, and we would adjust the idle mixture using idle mixture screws, and we would adjust main metering and secondary metering by changing out internal carburetor parts and/or adjusting A.P.T..  The secondaries don't have any jets.  You can do more heavy mods to correct idle mixture if your engine is heavily modified and runs with low vacuum.

I don't know if this will help or just scare you, but here is a list of the things on a Q-jet that would be routine to adjust, from the shop manual in the late 70's.  It varies a little bit by application.  MOST Of this list has to do with cold operation, and wouldn't have any effect at all on how the car runs when it's warm.  This tells you a lot about carburetors.

#'s 1, 2, 12, 13, 14, and 15 would make a difference on a warm engine.

1.  Float Level.  This is fundamental, of course.  You bend the float arm.
2.  Accelerator pump volume.  You bend the pump lever.  You can use the "other hole" but that is not considered fine-turning, ha ha.
3.  Choke Lever Rod.  There is a kink in the rod going up to the choke that you can bend.  This just determines where the gizmos inside the choke coil would be located when the choke is closed.
4.  Fast Idle.  Finally, something you can adjust with a screwdriver
5.  2nd step Fast Idle (I wouldn't bother with this one) You bend the fast idle cam to determine "when" it would be on the 2nd step
6.  Air Valve Rod - this is for Q-jets with a rod connecting the front vacuum break to the secondary air valve.  It's kinked and you bend it.
7.  Front vacuum break.   Pull the choke open when you crank up.  This is important. 
8.  Rear vacuum break.  Opens the choke "a little more" on the first day of spring, or a full moon.  Not so important.
9.  Choke Coil.  This is basic.
10.  Choke Unloader adjustment.  This determines how far the choke opens when the engine is cold and you floor the accelerator.  You bend it.
11.  Secondary Lockout Adjustment - This determines how warm the engine gets before the secondaries will work.  You file the end of the pin down. (can't make this stuff up, can you?)
12.  Secondary Closing Adjustment -  This determine where are the primaries when the secondaries start to open.  You bend it.  Twice.
13.  Air valve spring adjustment - determines how much fuel gets sucked in while the air valve is opening above the secondaries.  This allows the carb to work without an accelerator pump in the back.
14.  Idle speed (warm).  You turn a screw
15.  Idle speed with the air conditioner on and a solenoid energized.


So you can see that it's important to know what it is you don't like about its performance.

« Last Edit: March 21, 2016, 07:00:51 PM by firebirdparts »
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pozarcar

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Re: How to rebuild a Quadrajet
« Reply #23 on: March 22, 2016, 06:24:18 PM »
I must here admit that my car still idles too high.  Frankly, I was just impressed that the carb didn't catch on fire since it was me who rebuilt it, so I haven't tried to fix the high idle beyond playing with the exterior adjustment screws a bit (which yielded no benefit).  Somebody advised to disconnect the choke, so I tried that by removing the choke lever rod, but no improvement so I put it back.  From observation it seems that my secondary butterfly (can remember the proper name, the "vanes" that open and close - the bigger ones - is that the secondary???) are open a bit too much at idle.  When I force them closed a bit the idle goes down until fully closed which stalls the engine.  Not sure if that is what I need to fix, and if so how.  Will have to tinker with it more when I break the car out of storage.
1978 Y-82 SE 4-speed (1 of 489)
2010 Plum Crazy Challenger SRT-8

Tyler

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addi1964

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Re: How to rebuild a Quadrajet
« Reply #25 on: April 12, 2016, 05:50:17 PM »
great i will give it a try have never had much luck with them

P-Js_BLKBRRD

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Re: How to rebuild a Quadrajet
« Reply #26 on: April 13, 2019, 09:35:55 PM »
"BLKBRRD" & "Friends"


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EscapeRacing

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Re: How to rebuild a Quadrajet
« Reply #27 on: April 27, 2019, 10:27:37 PM »
Post could not have come at a better time. Funny how that works.

dmont

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Re: How to rebuild a Quadrajet
« Reply #28 on: October 10, 2019, 12:40:19 PM »
Resurrecting an old post....I need to rebuild my carb on a '79 with an Olds 403.  Looks like the OP's link is no longer active on the Bandittransamclub site.  Can anyone recommend online resources for this task?

Maryland Bandit

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Re: How to rebuild a Quadrajet
« Reply #29 on: January 06, 2020, 02:35:13 PM »
By the way, I still have the tools, the time, and the knowledge to rebuild the Q-Jet. I'm not a 'name' guy, and I fly under the radar. Best suggestion is get your parts kits from Cliff's High Performance. They are THE best kits out there, period! He tailor makes the kits to your engine specs. Jets, rods, ect. I have the tooling to replace the throttle shaft bushings also. He will include bushings extra when you order your kit. Takes me about 3 weeks to tear one down, hot tank all the parts, polish the internal brass ones, modify any ports and install idle shaft tubes. and reassemble it. Ships back UPS ground. PM me for specific prices on certain operations. Not polite to discuss business out on an open forum. Thanks
Carbs weigh 15 pounds to zip 21771

darrylta

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Re: How to rebuild a Quadrajet
« Reply #30 on: March 25, 2020, 12:33:13 PM »
I was looking at Paul Spotts website and saw that he offers Quadrajet
rebuilds for $300.00. His attached photo depicts them to be correctly colored as well.
Cliff's rebuilt my last one, he did a great job on it for big bucks and a long wait.
Darryl

Re: How to rebuild a Quadrajet
« Reply #30 on: March 25, 2020, 12:33:13 PM »
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