Carburetor - ROCHESTER E4ME & E4MED 4-Bbl: Description

The E4ME and E4MED carburetors are of a 2-stage, downdraft design. Each bore has a triple venturi system. The secondary side is composed of 2 large throttle bores, using the air valve principle, in which fuel is metered in direct proportion to the amount of air passing through the secondary throttle bores. A baffle is attached to the secondary side of the air horn, above the main well bleed tubes. This deflects incoming air to improve secondary nozzle operation on heavy acceleration.

The E4ME and E4MED carburetors use an electrically-actuated choke assembly, and 2 vacuum break diaphragm assemblies, the front and rear. Both models are used in conjunction with the Computer Command Control (CCC) System. The carburetors are equipped with an electrically-actuated mixture control solenoid mounted in the float bowl. Fuel metering is controlled by stepped metering rods that operate in removable jets.

The E4MED model carburetor incorporates a float bowl mounted dual capacity fuel pump and a combined mixture control/dual capacity pump solenoid assembly. When the engine is cold, more fuel is necessary to ensure a smooth transition from idle to part throttle. When the engine is warm, less fuel is required. The dual capacity pump is controlled by the coolant temperature sensor. When coolant temperature is approximately 170°F (77°C), a solenoid within the carburetor is energized, opening a by-pass valve. This lowers the capacity of the pump by about one-half.

All models include tamper-resistant factory settings of the mixture control solenoid rich mixture stop screw and lean mixture screw, idle air bleed valve, TPS, ISC, ISS and idle mixture screws. No attempt should be made to adjust these except during major overhaul or replacement of air horn, float bowl or throttle body. Both electric and hot air chokes have riveted covers which must not be removed except for major overhaul.

These carburetors may be equipped with an Idle Speed Control (ISC) on the fuel bowl. Controlled by the ECM, the ISC controls the normal curb idle speed and acts as a dashpot on deceleration and throttle closing. On vehicles without an ISC, but with air conditioning, an Idle Speed Solenoid (ISS) maintains a specific idle speed during A/C operation.