DESCRIPTION
1. DESIGN
with slight modifications it is adaptable for use with other types of spark advance distributors.
Holley Carburetor Model 885-FF is a dual concentric downdraft carburetor with a side air inlet, designed for engines of approximately 230 to 500 cubic inch displacement. The side air inlet feature eliminates the necessary overhead space for the air cleaner on conventional carburetors in keeping with the growing tendency for lower hood design.
The dashpot, an anti-stall device, is incorporated in carburetors for use on vehicles with automatic transmissions.
2. APPLICATION
The series 885-FF carburetor is manufacturedto specificationfor several manufacturer's.
This carburetor contains many of the same design features found in other Holley Carburetors. The main fuel flow is metered by individually flow tested fixed jets. The extra fuel necessary for high power output is delivered by a fully automatic vacuum-operated piston type power enrichment system. The accelerating pump incorporates a spring over-riding feature which prolongs the discharge of accelerating fuel to provide a smooth, positive pickup.
For specific carburetor applications tothese vehicles, refer to the Holley Carburetor Parts Catalog for the specific user.
3. MAJOR SUBASSEMBLIES
Model 885-FF carburetors are composed of three major subassemblies: The air horn assembly, the main body assembly, and the throttle body assembly.
The carburetor if fully sealed and balanced to provide fuel-air ratio mixtures consistentwith engine power demands. All bleeds and vents are supplied with filtered air from the air horn and all fuel must pass through the fuel inlet strainer. This feature holds down to a minimum the accumulation of foreign deposits in the carburetor passages.
Some models of carburetors also contain interconnected vacuum passages which provide a balanced vacuum for control of spark advance mechanism of the Holley Pressure Distributor. In addition, this carburetor is designed so that
The die-cast airhorn contains the power valve piston and stem assembly, air bleed passages and the choke mechanism. The main body assembly contains the fuel inlet and float system, accelerating pump assembly and all the metering parts except some air bleeds and the idle adjusting needles. The throttle body assembly contains the throttle mechanism, the idle adjusting needles, distributor advance vacuum passages and the dashpot for vehicles equipped with automatic transmission. The governor is also an intergal part of the throttle body on the carburetor for governor driven trucks.
OPERATION
1. FUEL INLET SYSTEM
Fuel, under pressure from the fuel pump, enters the carburetor through the fuel strainer, a fine wire mesh screen. It then travels up the leg of the main body to the fuel inlet valve where the flow into the float chamber is regulated by the float, and the fuel inlet needle. The twin floates, hinged to a single float lever, float on the surface of the fuel in the float chamber. The fuel inlet needle which rides on the floattab, rises andfalls with the rise and fall of the floats. When the fuel level in the chamber drops, the floats drop, permitting the inlet needle to move away from its
seat, allowing more fuel to flow into the float chamber. As the fuel level rises, the floats and fuel inlet needle also rise to reduce the flow of fuel into the float chamber. Under actual operating conditions there is little travel of the floats and needle. Instead, once the proper fuel level is reached, an intermediate position is assumed bythefloatsand inlet needle permitting only the same amount of fuel to flow into the float chamber that flows out of the float chamber into the metering systems.
A sensitive float balance spring adds stability to the floats by absorbing shocks and vibration encountered over rough terrain.