Automotive Carburetion Made Easy



BASIC CARBURETION Continued

		The main metering jet meters suffi-cient fuel for operation in the econ-omy range. However, when more power is required, the carburetor must provide a richer mixture. In the economy range manifold vac-uum holds the power piston up, thus leaving the power valve ball check on its seat. As more power is re-quired, such as on rapid acceleration or hill climbing, the manifold vacuum drops. When this happens, the power piston spring forces the power piston down, unseating the ball check, and permitting addi-tional fuel to flow through the power restriction into the main fuel channel.



In the idle range there is insufficient suction at the main discharge nozzle to cause fuel to flow. However, the high suction in the mani-fold is utilized by drilling discharge holes in the carburetor beneath the throttle valve. A main fuel channel connects these holes to the float bowl. In the idle range these	holes, under high suction, supply fuel for smooth operation. As the throttle valve is opened the suction at these holes decreases and they stop feeding fuel. The timing is such that the main discharge nozzle starts feeding fuel at the same time the idle holes stop feeding.

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