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and a still richer mixture for a smooth idle and low
speed performance. In order to supply the correct
mixture to the engine under all operating conditions,
the Holley Carburetor Model 1904 has four basic fuel
metering systems. These are the main metering
system, the idle system, the power enrichment system,
and the accelerating pump system. In addition, there is
a fuel inlet system which provides the four basic fuel
metering systems with a constant supply of fuel, and
the choke system which provides a means of tempo-
rarily enriching the mixture to aid in starting and
running a cold engine.
The fuel inlet system provides the four basic fuel
metering systems and the choke system of the
carburetor with a constant supply of fuel. This fuel,
under pressure from the engine's fuel pump,
enters the carburetor through the fuel inlet needle valve
and seat assembly and flows into the float chamber. The
float, rising and falling with the fuel level in the float
chamber, moves the fuel inlet needle in relation to its
seat to regulate the amount of fuel entering the
carburetor. When the fuel in the float chamber reaches a
specified level, the float moves the needle valve to a
position to restrict the flow of fuel. Only enough fuel to
replace that being used will then be admitted. Any slight
change in the fuel level causes a corresponding
movement of the float, opening or closing the fuel inlet
needle valve to immediately restore the proper fuel
level. The fuel inlet system must constantly maintain
this specified level of fuel because the basic fuel
metering systems are calibrated to deliver the proper
mixtures when the fuel is at the specified level only.
A spring and pin inside the hollow fuel inlet
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