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Carter carburetors are an older type of vehicle carburetor found in a wide variety of classic car models; they can be found in everything from the Studebaker to Dodge pickup trucks. Since these carburetors are so old, you need to approach necessary repairs on them in a slightly different way. When undertaking this challenging project, following a few tips will make the process much easier.

Before Rebuilding

Before rebuilding the carburetor, take it apart completely and thoroughly clean all of the pieces. Often, so much dirt and gunk will build up in these old carburetors that you will not see a marked improvement unless you do this. Among the spots in a Carter carburetor that can get the most built-up are bleed vents, so make sure to get these as clean as you can. The best way to clean the parts is to soak them in carburetor cleaner overnight.

Cleaning Tools

Before putting the pieces together, take them out of the carburetor cleaner and brush them down with a wire brush, then blow the carburetor off with compressed air. Make sure to blast air through every hole in every component of the carburetor possible, including the needle valves, float valves and bleed vents. If you do not own an air compressor, a bicycle pump makes a good substitute. An ultrasonic cleaner is another cleaning option, especially for extremely dirty pieces.

Throttle and Choke Shafts

When cleaning the throttle and choke shafts, use care. These pieces must maintain their shape as closely as possible. If they lose too much metal due to excessive scrubbing, you may find yourself dealing with a vacuum leak.

Rebuild Kit

Buying a rebuild kit is a good idea for rebuilding a Carter carburetor. Many books and kits are available that have extensive information on Carter models, right down to how to manufacture your own components. However, sometimes you may find your kit disagreeing with the manual for your vehicles chassis. Always follow the manual in such a situation.

Fuel Fitting Installation

If you are installing a new fuel fitting on your Carter carburetor, it is very important that you replace the old gasket. If you forget to do this, you will deal with a host of problems with your float settings.

Idle Mixture Screws

Your idle screws set the amount of vacuum in your idle mixture. When you turn them clockwise, or inward, you lean the mixture, and when you turn them counter-clockwise, or outward, you enrich the mixture. Sometimes, during the course of a carburetor build and adjustment, they may be turned several times, but when you are finished, they must both be set the same number of turns from their seated position in order for the engine to run smoothly. Theore, it is important to always be aware of how many turns they are away from their seated position.

Float Height Adjuster

Float height adjustment is the most difficult part of your carburetors assembly. A way to make setting this a little easier is to use a drill bit as the adjuster. Many Carter carburetors have a factory float height of 25/64 of an inch. If you have a drill bit of this diameter, you can lay it across the top of your carburetor to set the float height.

Carburetors deliver a combination of air and fuel to internal combustion engines. These components use intake and exhaust valves to divide and transport the air-fuel mixture into the engine. The Rochester carburetor came about in 1965, when General Motors (GM) began using them in its vehicles with eight-cylinder engines; GM continued to install the carburetors in its vehicles for nearly 20 years. As of 2011, you can purchase an aftermarket Rochester carburetor, also called a Quadrajet.

Rochester B

The Rochester B carburetor had a float level of 1.28 inches and a float drop of 1.75 inches. The idle vented at 0.05 inches with the engine stopped in an idle position and the choke open. The Rochester B had a bowl vent of 3 internal and 1 external idle, while the 292 version had a bowl vent of 2 internal and 1 external idle. The throttle bore measured 1.563 inches for the Rochester B, but 1.75 inches for the 292 version. The main venturi for the 230 Economy version measured 1.063 inches, the main venturi for the 230 P and 230 version measured 1.594 inches and the main venturi for the 292 version measured 1.625 inches. The small venturi for all Rochester B versions measured 0.594 inches. The Rochester B pump discharge jet measured 0.031 inches, while the 292 versions measured 0.035 inches. The idle speed jet measured 0.067 inches, while the 230 Economy versions measured 0.057 inches.

Rochester 2G

The Rochester 2G had a float level of 1.359 inches and a float drop of 1.906 inches. It had a bowl vent of 1 inside. The throttle bore measured 1.438 inches, while the pump discharge measured 0.026 inches. It had main venturi of 1.094 inches and a small venturi of 0.125 inches. The main metering jet measured 0.053 to 0.054 inches.

Rochester 4G 348 and Rochester 4G 409

The Rochester 4G 348 had a primary float level of 1.625 inches and a secondary float level of 1.688 inches. It had a float drop of 2.25 inches and a bowl vent of 2 inside. The throttle bore measured 0.438 inches, and the primary discharge jet measured 0.026 inches. It had a primary main venturi of 1.125 inches and a secondary main venturi of 1.25 inches. The small venturi measured 0.25 inches. The 348 versions primary main metering jet measured 0/055 inches, while the secondary main metering jet measured 0.069 inches. The 409 versions main metering jet measured 0.054 inches, and the secondary main metering jet measured 0.067 inches.

Idle Specifications

The idle speed jet for the Rochester B measured 0.067 inches, while the 230 economy version measured 0.057 inches. The Rochester 2G 283 versions idle tube measured 0.028 inches, the 327 versions measured 0.031 inches and the 348 versions measured 0.037 inches. The Rochester 4G carburetors primary idle tube measured 0.027 to 0.028 inches, and the secondary idle tube measured 0.040 inches.