Holley 2300C, 4160, 4160C carbs

in a stable position. The float chamber is vented internally by the vent tube at all times. At curb idle or when the engine is stopped, the chamber is also vented by the external vent on top of the primary fuel bowl on some models. This external vent provides a release of excess fuel vapors from the bowl into the engine compartment instead of into the intake manifold.		needle which controls the mixture delivered at idle. Turning the needle out increases the volume of the mixture by allowing a greater flow of the fuel-air mixture.

		From the idle adjusting needle cham ber, the fuel goes through a short passage in the main body and down another passage into the throttle body. The fuel is discharged into the throttle bore below the throttle plate.

B. IDLE SYSTEM - GENERAL INFORMA TION - These carburetors utilize two identical idle systems, one for each primary barrel. Since the two passages function identically, only one side will be considered. At idle, the normal air pres sure in the float chamber causes the fuel to flow through the idle system to the greatly reduced pressure area below the throttle plate. Fuel flows from the float chamber through the main jet then into the small angular but horizontal passage (idle feed) that leads across to a vertical passage.

		(2) IDLE TRANSFER PASSAGE -During off-idle operation when the throttle plate is moved slightly, the fuel flows from the metering body into the main body passage and then into the throttle body passage. As the idle transfer slot is exposed to manifold vacuum, fuel is discharged into the throttle bore.

		As the throttle plate is opened wider and engine speed increases, the air flow through the carburetor is also increased. This creates an increased vacuum in the venturi to bring the main metering system into operation. The flow from the idle system tapers off as the main meter ing system begins discharging fuel. The two systems are engineered to provide smooth gradual transition from idle to cruising speeds.

Fuel flows up this vertical passage (idle well) past the idle feed restriction. The fuel then flows through a short horizontal passage and is mixed with air coming in from the idle air bleed. This fuel and air mixture flows down another vertical passage. At the bottom of this passage, the fuel-air mixture branches in two directions, one through the idle discharge passage and the other to the idle transfer passage.

		(3) MODEL - 2300, 2300G - Some appli cations are as previously described but on other 2300, 2300G applications the idle needles may be located in the throttle body.

(1) IDLE DISCHARGE PASSAGE - Fuel flows past the pointed tip of the idle adjusting



	Three Types Needle and Seat Assemblies