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Old 01-07-2013, 08:53 PM   #1
XQIZT
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Rochester Q-Jet Rebuilt - by a rookie

Well, the 77 needed it's carb rebuilt. Just old and tired (like a lot of the rest of the car). Kept loading up with gas and stalling upon exiting the highway after longer (hour plus) drives. Let me say, I know little to nothing about carburetors of any kind, so this was all new territory for me.

So, here's a bit of a step by step (from the VERY beginning) with some photos. Sorry, they are quick cellphone shots, but you get the idea.

First, before I touched one single thing, I read...a LOT. Here, books, articles online. Cliff Ruggles' book "How to Build and Modify Rochester Quadrajet Carburetors" was an excellent read for a beginner like me. I HIGHLY recommend this (or any other book you like) to go along with this write up, as I don't intend this to be the ultimate guide to carb work.

So now, ya just gotta dive in. Go slow, double check everything. Nothing in this procedure requires any more force than a couple of gentle taps with a rubber mallet.

So here we go:

First, prepare your work area. There are LOTS of tiny bits that can easily roll off your work bench so get a cheap cookie tray to set the carb in while you are working. The shallow lip will keeps things from disappearing. I got 2. One for the carb to rest in and one for the parts.

You'll also need a block of wood to place the carb on, so that nothing gets dinged up. Some linkages are lower than the flat plane of the base plate.

I also used sandwich bags to place parts in. Labeling with a Sharpie marker ensures nothing gets lost, everything gets put back in its place and you have no spare parts in the end.

Your carburetor lives under the air filter. If you don't know how to get the air filter off, or don't know which part in this photo is the air filter (and housing)...STOP NOW.


Here it is:


I started by carefully disconnecting all the hoses and lines attached to the carb. I took photos of each and it was pretty simple to reattach each in the correct place since all are pretty "set" in their bend and basically point right to the correct connection place. But I photoed in an overabundance of caution.

I found that to get the brake booster line easily clear of its port, I had to take off the 10mm bolt that holds the hard line to the throttle cable bracket.


Once all the lines are off, remove the 4 bolts (1/2inch socket) and with a few light taps, the carb should come free. Keep it flat and move to your work bench. Cover the gaping hole one the top of your motor (just in case).

I took a good look at everything and photoed as much as I could so if there were any questions during reassembly, I'd have a reference.

The kit I bought was from AutoZone, and it was fairly complete. The 2 additional parts I bought were a new float and a new fuel filter. Apparently, floats eventually soak up some fuel, so they get naturally "uncalibrated" and since they are cheap, why not just replace it?

Depending on your year and exact carb, there are various "accessories" attached to the sides of the carb (chokes, vacuum pull-offs, etc). Get them all off as much as possible, since cleaning involves some dunking and spraying with carb cleaner. Purely mechanical linkages I left on as much as possible, so i didn't have to worry about the need of possibly re-calibrating/re-adjusting them later.

First, get the airhorn (upper most portion) off. First you have to disconnect the accelerator pump arm. Drive the pin back just far enough so it comes loose, then take off the linkage.




Your choke linkage also needs to be disconnected. On the 77, the screw holding the arm comes off, then the linkage comes out of the arm.


The linkage can be left in place, as the airhorn will lift around it. Also take off the secondary metering rod attachment. Unscrew it and it all lifts straight out. On the 77, the airhorn is held on by 9 screws. Some are different lengths, so remember where each goes. Remember...labeled bags! Then lift the airhorn STRAIGHT UP. There are lots of delicate tubes hanging down from the airhorn that can be bent if you lift at odd angles.


Depending on which side the gasket sticks to, your primary metering rods maybe held to the airhorn (as mine were) or still in place in the main fuel bowl (middle portion of the carb). If they were like mine, disconnect them (with the arm) and be careful with them. There's also a spring that probably stayed in the cavity of the main fuel bowl. That can be removed as well.

Now you're in the heart of the beast. My accelerator pump plunger just came right out. The spring below it stayed in place. Take out the plastic filler piece to expose the float fulcrum. The float, fulcrum and needle all lifted right out.


The screw between the accelerator pump cavity and the primary metering rod arm holds down the check ball. Take out that screw and flip the whole carb over to get the checkball out. Do this over a catch pan, since there is likely a bit of fuel still in the carb.

For thorough cleaning, I removed the adjustable part throttle screw. If you opt to do this (the rebuilt kit instructions say not to) you will need to make a special tool. I cut the end off a cheap "furniture assembly" tool, then notched it with a Dremel.


For reassembly to "stock" settings, the APT should be 2 turns UP once you fully (and gently) screw it all the way down. Do this right the first time, because you can't access this screw once the carb is fully reassembled (unless you modify the airhorn).

Once all the parts are out of the main fuel bowl, flip the whole carb over and unscrew the 2 screws which will allow the base plate to be separated from the main fuel bowl.


Now your pretty much down to bare bones....start cleaning.

Assembly is reverse of what you just did...CAREFULLY. Especially the primary metering rods. You want them to slip into the primary jets, but you can't see it easily because the float is in the way. Just be patient because you don't want to bend the tips. One of mine was and I gently straightened it out.

Kits come with several gaskets in order to make them "universal" so make sure you are using the right ones.

The idle screws were all out of whack on mine. Screw them all the way in and then back them out 2 1/4 turns as a good starting point.

I had to fiddle with the choke setting to get it right. It was no where near where it was before the rebuild.

Have all your reference materials handy and you should be fine. Remember, I've NEVER done this and in about 6 hours, I had it apart, cleaned, reassembled and running. Admittedly, I had to take it off the car a second time and readjust the adjustable part throttle and float level, since I didn't get it right the first time.

Now, it idles in Park at 900RPM...in Drive at 750RPM. No hesitation, no stumble and so far...no stalling

How'd I do? I have plenty of other photos and can try to answer any questions that anyone may have.

Q-jets get a bad rap, but on a stock motor, it seems to be just fine.
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Old 01-07-2013, 10:55 PM   #2
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Great write up and your photos are better then most!
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Old 01-08-2013, 05:00 AM   #3
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YEP LOVE my Qjet. good write up.
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Old 01-08-2013, 06:42 AM   #4
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Well done! I did this procedure many times back in the day - first on my '66 442 and then several times on my '74 and '77 vettes. For some reason, those quadrajets constantly got to a point where there was bad bog down on acceleration. New accelerator pump fixed it for a while, but I would do a complete disassembly and clean-up each time I needed to replace the AP. I'm not sure I was ever smart enough to use a lip pan, because I remember chasing springs and ball bearings all over the garage.
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Old 01-08-2013, 04:45 PM   #5
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call cliffs and get a new accelerator pump kit from him or you will have a problem. ask cliff why
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Old 01-08-2013, 05:45 PM   #6
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Great job XQIST. I new you could do it.

Hey 7t9l82 Who is Cliff and why is his acc pump better than the one that comes in the kit. I have never had trouble with an acc pump not pumping?
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I can't tell if I'm dealing well with life these days or I just don't give a shit any more.
Old 01-09-2013, 09:24 AM   #7
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Thanks guys. I did have to readjust the choke. I put it where I THOUGHT it should go...big mistake. Put it right on the index mark (if your is adjustable) and call it a day.

Here's a good simplified write up on general adjustments for the choke (and the advice was dead on):
http://www.chevelles.com/techref/Adj...tic_Chokes.htm


Thank you for everyone that offered help and gave words of encouragement. There's always that split second of "hold on to your butts" just before turning the key that makes me worry.
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Old 01-09-2013, 10:55 AM   #8
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Here is a Q-jet story from hell that I lived about 1977. My wife and I had been doing a lot of spring and summer backpacking (it was big in the 70's), and we wanted to try our hand at a little winter backpacking. We loaded our '74 Vette with our Golden Retriever, put the packs on the luggage rack and headed for Santa Fe, NM in January. When we got to a trailhead at a campground (closed for the winter), the ground was frozen solid and there was about 6" of snow on the ground. We were at about 9000 ft. As soon as it got dark, the temp started dropping and it started snowing.....hard. We slept in our two man tent with the dog and by morning the temp was 15 degrees and there was over a foot of new snow. I also was developing Strep Throat and had fever and chills. We decided to pack up and head home, so while she packed, I started the Vette to warm it up. Uh-Oh, there was a problem. The choke was completely closed and the car would start, exhaling tons of smoke, but if I took my foot off the gas, it would die. The only way to keep it running was to keep the RPM up. I thought if I did this a few minutes, the choke would open, but it didn't. No matter what, the car would die if I tried to put it in gear or take my foot off the gas. I was desperate to get out. There were no humans on the mountain except us and the snowplow that had come through earlier and left. I got out my tools, took my gloves off and in 15 degrees started disassembling the choke mechanism. The valve was stuck closed and I could not open it. I finally had to remove the screws that actually hold the valve plate onto the shaft. Not easy because the screws are swedged on (or maybe locktite - it's been a long time) so they won't vibrate off. With blue, frozen fingers I managed to get the screws out without dropping them down the intake, and got the valve plate off. The car ran fine at that point and we headed down the mountain. By the time we got to the interstate, it was black ice and cars were going off the road everywhere. In addition, going down the mountain about 5000 feet when my ears couldn't equalize pressure made my eardrums feel like they had ice picks stabbing them. Fortunately, after about 50 miles on IH40, the snow and ice turned to rain and we average about 85 mph for the 10 hour drive home. We never went ice camping again.

Last edited by Texdentist; 01-09-2013 at 11:47 AM.
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Old 01-09-2013, 02:02 PM   #9
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Wow TxDentist what a Ordeal but Luky you got it to run after all that.. If it had been one of todays cars U would still be there... Ha Ha
Desperate times calls for Desperate measures..

It was a Nice read and I could visually see all that was happening while I was reading your story.
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Old 01-09-2013, 07:42 PM   #10
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cliff ruggles at cliffs performance wrote the book on the quadrajet. there has been several failures of accelerator pumps in current kits, even the napa kits fail with the ethanol in the fuel. cliff makes his own accelerator pumps that hold up. believe me its nobody's imagination. this is a serious potentially dangerous issue. i would advise anyone with a quadrajet to investigate this further
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Old 01-10-2013, 05:41 AM   #11
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I think my q jet has got a genuine leather bucket acclerator pump in itdam it must be old.
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Old 01-11-2013, 05:21 PM   #12
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Quote:
Originally Posted by Texdentist View Post
Here is a Q-jet story from hell that I lived about 1977. My wife and I had been doing a lot of spring and summer backpacking (it was big in the 70's), and we wanted to try our hand at a little winter backpacking. We loaded our '74 Vette with our Golden Retriever, put the packs on the luggage rack and headed for Santa Fe, NM in January. When we got to a trailhead at a campground (closed for the winter), the ground was frozen solid and there was about 6" of snow on the ground. We were at about 9000 ft. As soon as it got dark, the temp started dropping and it started snowing.....hard. We slept in our two man tent with the dog and by morning the temp was 15 degrees and there was over a foot of new snow. I also was developing Strep Throat and had fever and chills. We decided to pack up and head home, so while she packed, I started the Vette to warm it up. Uh-Oh, there was a problem. The choke was completely closed and the car would start, exhaling tons of smoke, but if I took my foot off the gas, it would die. The only way to keep it running was to keep the RPM up. I thought if I did this a few minutes, the choke would open, but it didn't. No matter what, the car would die if I tried to put it in gear or take my foot off the gas. I was desperate to get out. There were no humans on the mountain except us and the snowplow that had come through earlier and left. I got out my tools, took my gloves off and in 15 degrees started disassembling the choke mechanism. The valve was stuck closed and I could not open it. I finally had to remove the screws that actually hold the valve plate onto the shaft. Not easy because the screws are swedged on (or maybe locktite - it's been a long time) so they won't vibrate off. With blue, frozen fingers I managed to get the screws out without dropping them down the intake, and got the valve plate off. The car ran fine at that point and we headed down the mountain. By the time we got to the interstate, it was black ice and cars were going off the road everywhere. In addition, going down the mountain about 5000 feet when my ears couldn't equalize pressure made my eardrums feel like they had ice picks stabbing them. Fortunately, after about 50 miles on IH40, the snow and ice turned to rain and we average about 85 mph for the 10 hour drive home. We never went ice camping again.
2 people, a dog, camping gear, and a foot of snow in a 74 vette! God man you do enjoy your car as intended!
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Old 01-14-2013, 08:55 PM   #13
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I've been rebuilding Q-jets forever and used tio be able to due them in my sleep. Oh these bring back memories.
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Old 01-15-2013, 07:42 AM   #14
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Quote:
Originally Posted by gtr1999 View Post
2 people, a dog, camping gear, and a foot of snow in a 74 vette! God man you do enjoy your car as intended!
I've had four and I drive them all that way. I bought it to drive, not look at.
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