9D-3 MODELS 2G-2GC-2GV PAGE 17

At normal engine speeds, the bleed valve in the distributor stays open and bleeds off the vacuum applied to the governor diaphragm, therefore, no governor action takes place. At higher engine speeds approximately 3800-4000 engine RPM where governing is needed, the centrifugal weight on the distributor bleed valve shaft closes the valve and vacuum is applied directly to the governor diaphragm. The diaphragm pulls the throttle valves closed against the governor spring tension to a position where the engine will not exceed the governed speed.

When power is required, as engine load is increased, the engine manifold vacuum will drop and allow the governor spring to open the throttle valve farther to increase engine speed.

SERVICE

FIGURE 26

The basic carburetor systems, and operation are the same as on the standard 2-bore carburetors, as explained in the previous text. Disassembly and assembly procedures are the same except for governor servicing.

the accelerator pedal is depressed, the throttle lever moves and allows the primary throttle valves to open. This is accomplished by the governor spring which holds a tang on the throttle shaft against the throttle lever. Therefore, the primary throttles actually follow the rotation of the throttle lever by the governor spring tension rather than being directly forced open, as on the conventional carburetor.

CONTROL VALVE

Whenever the distributor is removed for overhaul, the governor control valve mechanism should be disassembled and cleaned.

In operation, manifold vacuum is supplied to the top side of the governor diaphragm through a passage in the housing which leads to manifold vacuum directly beneath the throttle vales. Calibrated restrictions are used in this passage to control the amount of vacuum applied to the diaphragm.

MAJOR SERVICE OPERATIONS

DISASSEMBLY, CLEANING, INSPECTION AND ASSEMBLY PROCEDURES

GOVERNOR BLEED VALVE OPERATION

The following disassembly and assembly procedures may vary somewhat between applications due to specific design features. However, the following will basically pertain to all Rochester 2-bore carburetors of the side bowl "G" design.

(Fig. 27)

AIR HORN REMOVAL AND DISASSEMBLY

(Fig. 28)

FIGURE 27

The centrifugal bleed valve, mounted in the ignition distributor shaft, is nothing more than a sliding valve which is normally held open by spring tension at low engine speeds. It closes at high engine speeds, as centrifugal force of the counterweight on the end of the valve shaft moves the valve outward and covers the bleed hole.

FIGURE 28