Genuine 1985 Chevrolet Caprice Carburetor

1985 Chevrolet Caprice Parts Questions & Experts Answers

• Q: What should be considered regarding the general application of different types of carburetors installed during the production on 1985 Chevrolet Caprice?

  A: Reference should be made to the general application of the different types of carburetors installed during the production run of vehicles covered, emphasizing that the information given is not intended to identify a particular carburetor with a specific vehicle; the actual carburetor fitted to your engine should be checked by recording the number stamped on the unit and verifying it with your partsman. It is crucial not to use an incorrect unit or modify the jets or internal components by substituting parts with different manufacturer's part numbers from those originally used. All units have automatic chokes, either stove (hot air) heated from the manifold or electrically heated. Depending upon engine capacity, the carburetor may be of dual or four-barrel downdraft type. Overhaul of a worn carburetor is not difficult, but always obtain a repair kit in advance, which will contain all necessary gaskets and replaceable items. If a carburetor has seen considerable use and is obviously well worn, it will probably be more economical to replace it with a new or factory reconditioned unit. The Rochester 2G series carburetor is a dual barrel, side bowl design, with units fitted to manual and automatic transmission vehicles being similar but varying in calibration. The main metering jets are of a fixed type, with calibration accomplished through a system of air bleeds, and a power enrichment valve assembly is incorporated to control power mixtures by air velocity past the boost venturi according to engine demands. On later model vehicles, an electrically-operated throttle closing solenoid ensures that the throttle valve closes fully after the ignition is switched off to prevent running-on. The choke is automatic and operated by an exhaust manifold heated coil. The Rochester 4MV (Quadrajet) series carburetor is a downdraft two-stage unit, with the primary side using a triple venturi system and the secondary side having two large bores and one metering system that supplements the primary main metering system. The Rochester M2M/E2M model carburetors are 2-barrel, single stage units of downdraft design, essentially the same as the primary side of the M4M series carburetors. The Rochester M4M/E4M (Quadrajet) series carburetors are 4-barrel, two-stage units of downdraft design, utilizing a triple venturi system on the primary side with 1 3/8 inch throttle valve bores, while the secondary side has two 2¼ inch throttle valve bores. The E4M series differs from the M4M series in that special design features for use with the C-4 system are included for optimum air/fuel mixture control during various stages of engine operation. The Holley 4150 series carburetor is a 4 barrel fitted to early high-performance vehicles only, featuring a center inlet with a temperature sensing choke coil mounted on the intake manifold.