In January of 2009, myself and two friends purchased a 1977 Chevrolet Monte Carlo Landau coupe for $600. Under the hood, it had a small block 350 V8 engine with a Rochester QuadraJet carburetor. The car ran but didn’t have much power. We were too focused on doing body work to worry about the engine at first.
In the summer of 2011, I decided to take a look at the rebuilding the carburetor. I found a couple of companies that offered rebuild services by mail. The cost seemed to be around $400 dollars – almost as much as we paid for the whole car!
Having ruled that option out, I looked at the cost of buying a Holley or other brand of carburetor. Again, the prices were way out of my range ($280 to $400). There was only one option left: to rebuild it myself.
This was my first time owning a carbureted car, much less working on one. Still, I figured that I could learn to do it as well as anyone else.
The first thing I did was scrub the grime off the side and locate the serial number. Stamped into the side of the carb were these numbers:
A quick Internet search revealed that we had a Rochester 4-barrel carburetor with a manual choke that met California emissions standards. The Julian date code (March 7, 1977) was correct for the year of the car, leading me to believe it is the original carb.
I purchased a rebuild kit from QuadraJetParts.com for our M4MC carburetor. It came with new gaskets, a needle and seat assembly, and some other parts for $30.95 plus a few dollars for shipping.
Next, I started looking for technical resources to help me out. The first thing I bought was the book How to Rebuild and Modify Rochester Quadrajet Carburetors by Cliff Ruggles (ISBN: 1932494189). This book provided a good background on Rochester Quadrajets as well as some common performance modifications. There was a section on fixing design problems with older Quadrajets, most of which had been corrected at the factory by the time our 1977 “Mod Quad” carburetor was built. This book was very useful in my understanding of how the Q-jet carbs work, and I would highly recommend it!
Next, I downloaded a copy of the Delco Service Manual 9D-5 (PDF) for Quadrajet carburetors from 1981. This book provides some great technical drawings as well as an overview of the rebuild process. It had some information none of the other references had, such as the pattern for tightening the bolts on the air horn. I also printed a blown-up version of the exploded parts diagram.
Finally, I used the website Ken’s Quadrajet as my main reference. I printed out every page and used it as my step-by-step teardown instructions. This was the single most useful resource I had, and the project definitely would not have happened without this page.
The Teardown Process
Armed with my new information, I set about removing the carb from the intake manifold. I disconnected the fuel and vacuum lines, taking care to label each one with masking tape. The Cliff Ruggles book had recommended placing the carburetor on a block of wood for disassembly.
I also bought a cookie sheet and covered it with a towel. This allowed me to move the project around and the towel kept the small pieces from getting lost. Then, I carefully began the disassembly process.
I must reiterate that going into this project, I knew nothing about carburetors or how they worked. However, I quickly became familiar with terms like choke, air horn, fuel bowl, metering rods, and the other components as I pulled everything apart. I discovered that the bottom plugs of the fuel bowl had been sealed, indicating that someone had rebuilt this carb previously.
As filthy as the outside looked, the inside was even worse! The bottom of the fuel bowl was filled with fine sediment and the primary jets were full of gunk. The passages for the needle and seat, check ball, and accelerator pump were also full of crud.
Cleaning and Reassembly
The best way to deep clean the years of grime was to submerge it in liquid carburetor cleaner. I picked up a gallon of Chem-Dip liquid carb cleaner for around $20. This is seriously nasty stuff! I am not the kind of guy who follows every little warning, but you really want to make sure to wear nitrile gloves and goggles when working with this stuff.
The carb cleaner also came with a plastic bucket to hold smaller parts. I left the air horn, fuel bowl, and smaller pieces submerged in the liquid cleaner for a day, then blew out all the passages with a can of spray carb cleaner and compressed air. I also cleaned the moving pieces with Liquid Wrench (note: Don’t use WD-40 here. Liquid Wrench is a lubricant whereas WD-40 is not). Wow, did that ever make a difference! Underneath all the grime, it looked great!
The inside of the carb also cleaned up nicely. Check out this picture of the fuel bowl and the primary jets (the two bronze things in the middle of the photo). Compare it to the photo above, and you can see just how much better everything looks!
I put everything back together with the new needle and seat, check ball, and gaskets from the rebuild kit plus a new fuel filter. It took some care to reassemble the linkages and to measure the float height during reassembly to make sure it was correct. When it was all said and done, I have to say that the carb looked pretty darn great.
With the carburetor reinstalled, we tried to start the car. We tried, and tried, and tried until the battery was dead. The engine would turn over but would not run. Searching for the symptoms of the car online, I found the answer: I pulled the carb off once more, moved the needle on top of the float valve, and reassembled it. Once that was fixed (and the battery recharged) the car fired right up!
With a little tuning from my friend Mike, we got our car to run pretty darn well. It starts up every time, idles smoothly, and even passed emissions! We will bring you more posts about the car in the future, but for now I hope you enjoyed this article about rebuilding a Rochester Quadrajet carburetor!