Description

The Model 16P12 carburetor is a horizontal plain tube type with a fuel bowl, a single ring-shaped float, an accelerating pump, idle mixture adjusting needle and a throttle stop screw for idle speed adjustment.

The throttle body casting contains an integral venturi and a fuel valve seat that is pressed into the body. The underside of the throttle body contains a long boss. The main jet and discharge tube assembly screws into the boss with the end of the tube projecting up into the venturi.

Idle System, Figure 3-68

The fuel for idle is drawn from the main metering well through the idle tube and is mixed in the channel leading to the idle discharge holes with air entering through the idle air bleed. At slow idle speed, the throttle plate is positioned as shown in Figure 3-68 to expose only the No. 1 idle discharge hole to engine vacuum. Air is admitted to the idle channel through the No. 2, 3 and 4 (late 1972) idle holes. This air mixes with the fuel-air mixture in the channel and is discharged through the No. 1 idle hole.

As the throttle plate is opened, the idle holes progressively discharge fuel-air mixture to supply the increased fuel required at the higher engine speeds.

The idle adjusting needle regulates the fuel-air mixture flowing through the No. 1 idle discharge hole. Turning the needle IN (clockwise) results in a leaner mixture. Turning it OUT (counterclockwise) provides a richer mixture. The idle speed is set by adjusting the throttle stop screw - not the idle adjusting needle.

Choke System, Figure 3-68

Before cranking the engine, the throttle should be opened to expose all three idle holes. The choke plate should be held fully closed during the cranking. After the engine starts, open the choke slightly. A hole in the choke plate helps to prevent over-choking when the engine is started. The choke should be moved to wide open when the engine is partially warmed up.

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Idlt Tub.

Figure 3-68. Idle ang Choke Systems

Idlt Tub.

Figure 3-68. Idle ang Choke Systems

High Speed (Main Metering) System, Figure 3-69.

The fuel for engine operation from off idle to full throttle range is supplied from the fuel bowl through the main metering jet, metering well and discharge tube. As the fuel flows through the metering well and tube, it mixes with air entering through the well vent to provide the correct fuel air mixture ratio for all engine speeds and loads. A series of air bleed holes in the discharge tube permits the air from the well vent to enter the bowl below the level of the fuel in the float chamber. This reduces the average density of the fuel and enables it to flow freely at low suction. At high engine speeds (and high suction), the proportion of air to fuel through the main metering system is reduced to provide the richer mixture needed for peak performance.

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Discharge Tube

Main Jet

├čjajp Mtttring

Figure 3-69. High Speed System ADJUSTING CARBURETOR (Figure 3-70)

S WiST"

Discharge Tube

Main Jet

├čjajp Mtttring

Figure 3-69. High Speed System ADJUSTING CARBURETOR (Figure 3-70)

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