Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level) - Hot Rod Forum : Hotrodders Bulletin Board
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Old 01-11-2011, 10:29 AM
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Rochester Quadrajet 4MV Carburetor: Removal, Disassembly, Rebuild (Rookie Level)

**If anything is mislabeled or the information is incorrect, please let me know! Thanks!


- Background -

I have a '77 Chevy pickup that became victim to water and debris in the gas tank (you can read up on that story here.)

At this point, due to the debris getting in the carburetor, it has to be rebuilt.

This is my first time rebuilding a carburetor as well as taking apart and putting together anything on a large scale.

The posts in this thread will be written in such a way as to provide a complete step-by-step documentation of everything I do (aka, sorry if this seems lengthy). This is for two reasons: 1) the other forum members who help out have all necessary information available and, 2) anyone of similar mechanical apptitude as me (which is very minimal) who finds this will be able to follow along without getting lost or intimidated.




- Research -

I began by searching all over the internet as well as local libraries for any guides that can walk me through this process.


I started by decoding the carburetor so I could purchase the proper repair kit. For Rochester, I used the following website: http://www.holisticpage.com/camaro/parts/carb.htm.


The code on this carburetor is 17057525 APP 3356. Based on the information provided by the website the carburetor is:
170 – Built: 1975 and onward by the Rochester Division of GM
5 – Decade produced: 1976 - 1979
7 – Year produced: 1977
5 – Model: Quadrajet (4bbl) California Standards
2 – Division: Chevrolet
5 – Transmission: manual (truck is an automatic)
APP- Customer code
3356- Build date code


With this information decoded, I moved onto to looking for guides on rebuilding these carburetors. Amazon carries a few titles on Rochester carburetors, but the most highly reviewed is “How to Rebuild and Modify Rochester Quadrajet carburetors” by Cliff Ruggles. It was also recommended by another forum member in another thread.


Aside from the book, I also found a couple of forums and websites where a rebuild had been documented. I found this one to be the most informative: http://www.vetteprojects.com/kstyer/quadrajet.htm


Another resource that may prove helpful is the original Delco manual that was uploaded online: http://www.tocmp.com/manuals/Carbs/Rochester/QJet/


Lastly, the one place that everyone can go to learn how to do practically anything is Youtube. Again, a few people took the time to create several videos to show how to rebuild a Rochester carburetor. Due to videos being constantly removed or updated, its best to go look for the newest materials.




- Removal -

The carburetor's removal comprised of the following steps:
1. Take pictures of the carburetor from every angle as it sits.
2. Label all hoses and connections to be removed. In this case, used masking tape since its easy to write on it.
3. Take pictures from every angle of the hoses as labeled.
4. Unbolt the carburetor and remove all hoses and connections (throttle cable, springs).
5. Remove the carburetor and take close-ups shots of everything.




Step 1:





Steps 2 and 3:





Step 5:










- Rebuild Kit -

I purchased a Hygrade brand rebuild kit and float. As warned in the other thread, the instructions do leave much to be desired.


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Old 01-11-2011, 11:02 AM
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That nut on the backside of the carburetor base plate, do not overtighten it. Use a thread sealant tape or paste on it and don't wrench down hard on it, the casting is thin and will crack if over torqued. you can pretty much get it tight by feel, the sealant allows you to tighten it with less torque and still have a good seal.
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Old 01-11-2011, 11:21 AM
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Hey Torque,

Quote:
Originally Posted by cyclopsblown34
That nut on the backside of the carburetor base plate, do not overtighten it. Use a thread sealant tape or paste on it and don't wrench down hard on it, the casting is thin and will crack if over torqued. you can pretty much get it tight by feel, the sealant allows you to tighten it with less torque and still have a good seal.
Glad you mentioned that because I have a bad habit of overtightening. Any idea what that hose is for?
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Old 01-11-2011, 12:14 PM
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with your permission, when you have finished the project, we'll put it in the knowledge base. Dan
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"When I was younger, I could remember anything, whether it had happened or not." - Mark Twain
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Old 01-11-2011, 12:48 PM
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Quote:
Originally Posted by lt1silverhawk
Hey Cyclops,



Glad you mentioned that because I have a bad habit of overtightening. Any idea what that hose is for?
My Bad! Sorry, I meant "Hey Cyclops" (so I fixed it here). Just got confused while responding and getting ready for work. You and Torque have both been very helpful though!





Quote:
Originally Posted by dinger
with your permission, when you have finished the project, we'll put it in the knowledge base. Dan
Yes, please do
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Old 01-11-2011, 12:49 PM
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That hose from that fitting generally goes to the brake booster. If it doesn't go there, somebody may have chosen to use it for the PCV. I'm not too certain about the way Mexifornia emissions are routed though.
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Old 01-11-2011, 12:59 PM
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Something you'll need to know for disassembly, on the driver side front, the accelerator pump, there is a fulcrum the actuator arm rocks on, there are I think two holes in it, note where the throttle linkage attaches to it. The instruction sheet will probably tell you where to attach it depending on which engine too. To remove the lever, just use a small diameter punch and push the roll pin out of the fulcrum point and lift the lever off. I did several Q-jet rebuilds, all the while cursing the way I had to twist the top of the carb to remove it, once I realized there was a removable pin, it made disassembly and reassembly a breeze.
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Old 01-11-2011, 12:59 PM
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Quote:
Originally Posted by cyclopsblown34
That hose from that fitting generally goes to the brake booster. If it doesn't go there, somebody may have chosen to use it for the PCV. I'm not too certain about the way Mexifornia emissions are routed though.
Hmmm, I know I removed a rubber hose from the carburetor that ran to the booster. And the hose from the PCV is rubber as well. Will give this one another look.

On a side note, I realized one of the gaskets in the repair kit was ripped. I was able to see it through the plastic cover and, even though I don't know if it is the one I need, I'll be exchanging it for another kit today.

By the way, any tips on how to properly disassemble a carburetor? Any particular way the parts should be organized or grouped when taken apart?
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Old 01-11-2011, 01:03 PM
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The line from that fitting is usually a steel tube that runs over to the booster.

Disassembly tips? Take lots of close up, well lit pictures of the linkages.
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Old 01-11-2011, 01:22 PM
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Quote:
Originally Posted by cyclopsblown34
Something you'll need to know for disassembly, on the driver side front, the accelerator pump, there is a fulcrum the actuator arm rocks on, there are I think two holes in it, note where the throttle linkage attaches to it. The instruction sheet will probably tell you where to attach it depending on which engine too. To remove the lever, just use a small diameter punch and push the roll pin out of the fulcrum point and lift the lever off. I did several Q-jet rebuilds, all the while cursing the way I had to twist the top of the carb to remove it, once I realized there was a removable pin, it made disassembly and reassembly a breeze.
If it is the part I think you are talking about (it was the only part that came close to making me cuss poetically), I believe I've got a picture of it up top labeled "Throttle Cable Location". It is held in place by a nut and screw. Otherwise, further guidance is needed.




Quote:
Originally Posted by cyclopsblown34
The line from that fitting is usually a steel tube that runs over to the booster.
Disassembly tips? Take lots of close up, well lit pictures of the linkages.
Good point, I may have to reshoot some of the pictures because they are rather dark.

My main concern is organizing everything properly before disassembly begins so the small parts are not lost or mixed up. At this point, I am planning on using a few one-gallon milk bottles, cutting off the top and using the bottom portion to hold parts. They may even be good for washing and soaking parts. If there is a better way to do it, please do mention it.
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Old 01-11-2011, 06:51 PM
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a cupcake pan works really well for organizing parts
i also use an old silverware tray for parts

nice post, alot of people will be able to use this
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Old 01-11-2011, 07:02 PM
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Hey Matt,

Quote:
Originally Posted by matts37chev
a cupcake pan works really well for organizing parts
i also use an old silverware tray for parts
That is actually a very good idea! Thanks for sharing.




Quote:
Originally Posted by matts37chev
nice post, alot of people will be able to use this
Thanks man . I do hope this comes in handy, especially for other rookies like me.
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Old 01-12-2011, 10:14 AM
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A Note On Carburetor Removal: Upon removal, be sure to turn it upside down to get any fuel out before placing it anywhere. Placing a couple of paper towels underneath it when setting it down on the work area is a good idea in case any left-over fuel pours out. Lesson learned.




- Disassembly Prep -

Quote:
Originally Posted by cyclopsblown34
Disassembly tips? Take lots of close up, well lit pictures of the linkages.
I took as many pictures as I could from every angle before I start taking apart the carburetor. I still expect to take more because Im sure I may have missed something (or it could just be the jitters of nervousness ).





For cleaning the carburetor parts, I went ahead and invested in a gallon of Berryman Chem-Dip Carburetor and Parts Cleaner. This is an example of "researching before attempting " paying off: My initial thought was to buy a dozen cans of carb cleaner and spray the gunk off 'em .






For you visual/auditory folks, I used this Youtube video as a guide while prepping. The author has done a disassembly and rebuild in several 10-minute segments.
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Old 01-12-2011, 06:22 PM
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Milk jugs will rapidly melt with carb cleaner. The muffin pans work great. As a technique, I use two pans and lable each "bin" and place the old part in one bin and at the same time, I place the new part in the other pan. Most kits are 'generic' so this is the best time to pick out the part that matches the removed part and set the residual parts aside. When it comes to little balls and seats, they can look the same, but it is a good ideal to mic the balls to make sure you select the same one. Soaking all metalic parts is the way to go but using small brushes lightly is a good ideal. Do not soak non-metalic items. You also need to use the correct size wire to run through all the jets and orifices. Be careful not to force the wire and score the surface. One last rinse with the cleaner and blow dry every thing. Make sure you use eye protection for this because the solvent can do serous damage!

I built a stand to hold the carb body so that I could functionally check all the linkage and clearances on the butterflies. It also makes assembly of the metering rods much easier. You can buy a stand, but hard to justify unless you plan on rebuilding lots of carbs. My Q-Jet book told me how to build the stand and it has been invaluable over the years.

Taking pics as you go is a good ideal, but my book is always open through out the process.
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Old 01-13-2011, 10:19 AM
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Hey trees,

Quote:
Originally Posted by trees
Milk jugs will rapidly melt with carb cleaner. The muffin pans work great.
I am glad you pointed that out. I was planning to use the plastic milk jugs to separate the parts only. Since the gallon-size carburetor cleaner comes with a handy dipping bucket, I was planning to soak the parts directly in there. Or is that a bad idea?




Quote:
Originally Posted by trees
As a technique, I use two pans and lable each "bin" and place the old part in one bin and at the same time, I place the new part in the other pan. Most kits are 'generic' so this is the best time to pick out the part that matches the removed part and set the residual parts aside. When it comes to little balls and seats, they can look the same, but it is a good ideal to mic the balls to make sure you select the same one.
I think that is an excellent technique, and especially beneficial for us first-timers who can easily get confused.




Quote:
Originally Posted by trees
Soaking all metalic parts is the way to go but using small brushes lightly is a good ideal. Do not soak non-metalic items. You also need to use the correct size wire to run through all the jets and orifices. Be careful not to force the wire and score the surface.
Buying the cleaning brushes is next on my list; no need to skimp out on the cleaning. Im sure the local parts shop has a good selection.




Quote:
Originally Posted by trees
One last rinse with the cleaner and blow dry every thing. Make sure you use eye protection for this because the solvent can do serous damage!
Garage door is wide open and goggles are ready to go!




Quote:
Originally Posted by trees
I built a stand to hold the carb body so that I could functionally check all the linkage and clearances on the butterflies. It also makes assembly of the metering rods much easier. You can buy a stand, but hard to justify unless you plan on rebuilding lots of carbs. My Q-Jet book told me how to build the stand and it has been invaluable over the years.
Speaking for myself, this is probably not the last carburetor I will ever build. Carb stands are not expensive ($20+), making one is a good idea too. One person made one himself using a 2x4, some long bolts and washers here. By the way, which book are you using?




Quote:
Originally Posted by trees
Taking pics as you go is a good ideal, but my book is always open through out the process.
There is just no substitute for a good book, but for now, I am making do with the online articles and Youtube videos. Hopefully I'll be adding at least one good title soon.




These are great tips trees and I'm glad and thankful you shared 'em!
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