The objective is cleaner emissions and finite power tuning and fuel efficiency. Not only that, but just about every corner auto parts store has a rebuild kit available, depending on the Rochester model you have. Or by special request, Dichromate finish can be applied. But, not all Quadrajet carburetors were built by Rochester. Check eBay, Craigslist and Racing Junk websites for options.
This new carburetor was blended with what Rochester knew about carburetors, mixed with ideas from other manufacturers, spread-bore design and vacuum secondaries. Non computerized, vehicle without closed loop system. Choke parts, primary metering rods and throttle shafts are not interchangeable between 4M and M4M carbs. New fuel filter between fuel pump and carb is required. We carry a complete line of domestic carburetors for passenger vehicles from 1972-1991 , including a variety of Holley ® and Edelbrock ® aftermarket carbs.
I had to modify the fuel line with flex hose for the fuel line. . Note the fuel wells, which have been opened, cleaned out, and recapped with an epoxy resin. Throwing another glitch in the program, is the fact that some Carter-built carburetors produced in the late 1960s might have been used on a different model year than the number shown on the carburetor. Fc Remanufactured Products known as Foreign Carburetors since 1974. I'm not patient enough to wait a year, and although I'm tempted to try a rebuild myself I don't want to add another variable to the mix. From the simple rebuild all the way to the complex, this book has it documented.
Those carburetors might very well have any of the above model numbers. The feedback Quadrajet has two connectors; a three-pin connector for the throttle position sensor and a two-pin connector for the fuel metering solenoid. Before you do any accelerator pump nozzle mods make sure you have the accelerator pump properly adjusted, including the correct duration spring for the job. The aftermarket offers a wide variety of main metering jets and rods. The trick is to know how to size these rods and jets for your application. Enthusiasts either love it or hate it.
This design is not unique to the Quadrajet. The power piston works like a Holley power valve spring pressure against manifold vacuum , allowing higher fuel flow through the power circuit as the throttle is opened. The trick is finding a good core you can build from. It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. The base plates are rebushed to remove excess wear from around the throttle shaft to stop certain vacuum leaks. If you are interested in doing some more reading, the Books Rochester Carburetors by Doug Roe, and Haynes Rochester Carburetor Manual by Mike Stubblefield and John Haynes are both very good technical resources for the rebuilding the Quadrajet. All bolts and linkage parts are plated.
Finding a compatible donor carburetor for your application should be relatively simple. Measure mid-float and tip of the float as shown. The primary wall of the 750 cfm unit does not have this bulge, and is consistent throughout. It should be noted that our testing was done with the supercharger disconnected. Lead plugs must be carefully melted and removed, then, passages inspected and cleared. On units made before mid-1968, the part number was stamped around the outside edge of a round metal tag attached to the fuel bowl.
We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more. Had we had the element of time, Gregg could have pushed the numbers closer to 550. So, a 4M is a Quadrajet, and a 2M is a two-barrel Dualjet. When you fire the engine, get the idle mixture as lean as you can while maintaining the most intake manifold vacuum possible. All carburetors for sale are and calibrated before leaving our carburetor rebuilding facility. Chevrolet Quadrajet carburetors would have a 0, 1, or even a 2. In fact, there have been a multitude of record-holding Super Stock race cars that have run in the 9-second bracket with a Quadrajet on top of their manifolds.
After saving all my hard-earned minimum wage money, I was off to the local speed shop to buy my new intake and shiny new performance carb. However, when you start making modifications such a hot roller camshaft, aftermarket induction and heads, and a host of other performance elements the Quadrajet struggles to keep up. It can also be air valve timing or main metering issues. Every carburetor is assembled by hand using a master rebuilding kit. As a side note, there was also a model 4M, that used a manually-operated choke.
The secondaries get a wet fuel charge from a fuel bleed above each secondary air valve plate. Plus we also carry a full line of Holley and Edelbrock Performance Carburetors. We also buy and swap old carburetors. Carburetors can warp from heat cycling, which calls for contact surface work. This is where the Quadrajet becomes challenging.