1942 - 1947 Chevrolet Shop Manual



	*6-42*

	gasoline out of the cylinder, closing the intake check valve and opening the discharge valve. The pump discharge then passes into the venturi through the main nozzle, Fig. 86. Low Speed At low speed the gasoline flows from the float chamber through the discharge check valve, through the main metering jet, thence to the main nozzle, Fig. 87. Suction on the down stroke of the engine piston draws air in through the air intake. This air passing over the main nozzle raises gasoline from the nozzle. The gasoline and air are then mixed in the venturi and pass through the throat of the carburetor to the manifold and cylinders, Fig. 87.	Full Throttle At the higher speeds, or wide-open throttle power operation, the manifold vacuum is reduced, allowing the spring in the vacuum cylinder to force the vacuum piston downward, causing the push rod to open the valve in the power jet, thus bringing it into operation. Fig. 88. This permits gasoline to flow from the power jet into the passage leading to the main nozzle, increasing the flow of gasoline over that passing through the main metering jet. REPAIR OPERATIONS Disassembly The following instructions cover the disassembly of the cab-over-engine carburetor: 1. Disconnect the link from the throttle valve to choke valve by removing the hairpin lock and washer. 2. Remove the three (3) screws from the bowl cover. The bowl cover should be removed with the accelerating pump parts attached. Fig. 89.


	Fig- 87—Main Jet Operation at Idle At intermediate speeds air enters the well surrounding the main nozzle through the main nozzle air bleed. This aids in lifting the gasoline as the gasoline level in the nozzle starts to lower with the increase in speed. During the operations described above, the high manifold vacuum impressed on the vacuum cylinder draws the piston upward, allowing the spring in the power jet to close the valve in the power jet.
		Fig. 8?—Bowl Cover Assembly 3. Compress the accelerating pump piston spring and remove the connector pin. Remove the spring, retaining spring and piston from the pump rod and plate assembly. 4. Remove the plug from the vacuum power cylinder, remove the piston and spring. 5. Remove the idle passage tube and idle adjusting screw from the carburetor upper body. 6. Remove accelerating pump sleeve and power jet push rod. Remove the float lever pivot pin and plug assembly, remove the float and needle valve. 7. Remove accelerating pump intake check valve, discharge check valve, and power jet. 8. Remove the main nozzle air bleed jet, idle jet, main nozzle, and main metering jet from the carburetor body.

	Fig. 88—Main Jet Operation at Higher Speeds