A fuel inlet needle valve clip connects the inlet needle firmly to the float tab. This prevents sticking of the fuel inlet needle due to gum deposits or impurities sometimes found in the fuel.
FUEL INLET SYSTEM
2. IDLE SYSTEM
In the idle range the air flow through the carburetor is too small to cause a great enough pressure drop in the venturi to operate the main metering system. However, the high manifold vacuum in this speed range provides a pressure difference sufficient to operate the idle system.
The atmospheric pressure in the float chamber forces fuelthrough the main metering jetinto the main well in response to the manifold vacuum at the idle discharge hole below the throttle plate. Fuel then passes into the idle tube through the calibrated restriction in the idle tube tip which meters the flow of fuel into the idle system. Air is introduced into the idle fuel by the idle air bleed as the fuel passes out of the idle tube and into the vertical idle passage. The fuel-air mixture then travels down the idle passage past the idle transf er hole which acts as an air bleed when the throttle plate is closed. The fuel-air mixture then flows throughthe idle adjusting needle orifice to be discharge hole into the main air stream in the throttle bore.
openings. This provides a smooth transition from idle to cruising speeds.
IDLE SYSTEM
3. ACCELERATING PUMP SYSTEM
Airflow through the carburetor responds immediately to any increase in the throttle opening, but there is a brief lag before the fuel inthe narrow passages can increase its flow to maintain the desired balance of fuel to air. The accelerating pump system operates during this period, supplying fuel until the other systems can once again provide the proper mixture.
The accelerating pump is actuated by the throttle lever to discharge fuel under pressure when the throttle is opened.
During off-idle operation the idle system functions the same except that as the throttle plate opens and exposes the idle transfer hole to manifold vacuum so that it also discharges fuel. The flow from the idle system tapers off as engine speed increases and manifold vacuum consequently decreases. At the same stage the main metering system begins to operate with increased throttle
When the throttle is closed, the pump piston travels upward in the pump chamber drawing fuel from the fuel bowl past the pump inlet ball check valve into the pump chamber. When the throttle is opened, the pump rod and horizontal arm move down in the piston stem slot to compress the pump spring. The compressed load of the spring acting on the piston, forces the fuel through the passage to the pump discharge valve The force of the fuel