Fuel enters between the needle valve seat and needle valve to fill the fuel bowl. The fuel flow is float controlled. Accordinly, the fuel level raises the float arm against the needle valve to the point where it seals against the valve seat and shuts off the fuel. As fuel is used by the engine, the level drops slightly, and additional fuel is admitted through the needle valve and valve seat. In actual operation, a fairly steady float position and fuel flow condition exists. The inlet system parts and the carburetor are of all-metal construction, except the needle valve which has a viton tip. A spring seperates the inlet needle valve from the operating pin to cushion the needle valve and float operation. An internal vent connects the fuel bowl to the air horn. Some external venting is effected through the pump lifter link slot in the main body casting.

ADJUSTMENTS AND SPECS

The instructions are a bit ambiguous on how to measure the float. The early type float and late type float are measured differently. Our problem is we don't know what the difference is. We assume we are selling the late type of float seeing the instructions were done in the 60's & 70's.

Bottom line is whichever one you use the float will be almost level when done.

Late 70's Nitrophyl Float Level

Carter YFA Float Drop

1981-85 Float Drop: 1 19/32"

FLOAT LEVEL ADJUSTMENT

1. Remove the carburetor air horn gasket from the carburetor.
2. Fabricate a float level gauge to the specified float level dimension.
3. Inver the air horn assembly, and check the clearance from the top of the float to the bottom of the air horn with the float level gauge. Hold the air horn at eye level when gauging the float leve. The float arm (lever) should be resting on the needle pin. Do not put pressure on the needle when adjusting the float. Bend the float arm as necessary to adjust the float level. Do not bend the tab at the end of the float arm. It prevents the float from striking the bottom of the fuel bowl when empty.

FLOAT DROP ADJUSTMENT

1. Hold the air horn upright and let the float hang free. Measure the maximum clearance from the top of the float to the bottom of the air horn with the float drop gauge. Hold the air horn at eye level when gauging the dimension.
2. To adjust, bend the tab at the end of the float arm to obtain the specified setting.
3. Install the carburetor air horn and a new gasket on the carburetor.

TROUBLESHOOTING

Vehicle Doesn't Run

Adding gas to the bore will get the engine running, but dies.

Obviously the carburetor isn't getting gas.

• Check the float drop. If the float isn't dropping, then the needle will not be pulled out of the seat and the float bowl will not fill up.
• Look at the tip of the needle. If any pressure was put on the needle when adjusting the float, then the needle may be damaged not allowing it to open.
• Test the fuel pump pressure. 4-5 lbs should do it.
• Did you replace the fuel filter(s).