Floats manage the flow of fluid through a device, primarily in pumps. A carburetor is a pump that serves two purposes, to pump fuel and air into the intake manifold, where the mix is delivered to the combustion chambers. Holley carburetors are designed with one to two floats, one for double barrel designs and two for 4-barrel designs. A Holley float can be adjusted on the fly without disassembly or detaching of the carburetor.
Place the car on a level surface and start it, letting the engine idle for 30 seconds. This allows the carburetor bowl to fill.
Turn the engine off. Look on the side of the fuel bowl(s) which is/are mounted on the front/back of the carburetor body, and find the fuel level sight port. Each bowl has a single port on its side, and may be a screw that requires removal, or a fixed plastic window. If it's a screw, turn it counterclockwise to remove it.
Rock the car back and forth while watching the sight hole/window. If it's a hole, fuel should just trickle from the hole. If it's a window, the fuel level should be just at the bottom of the window and no higher. If the fuel is too high, the float will need to be lowered, or raise for a low fuel bowl level.
Locate the float valve adjustment screw and nut. Turn the screw out two turns and pry up on the adjustment nut with a flat head screwdriver. With the engine running, turn the adjustment nut clockwise with a wrench to lower the float or counterclockwise to raise the float, while at the same time keeping the adjustment screw stationary with a screwdriver.
Watch the fuel level port hole or window until the fuel rests at the base of the window or hole. This indicates the float valve is adjusted properly.
Keep the adjustment nut stationary while retightening the adjustment screw. Once tight, reinsert the fuel level sight plug screws if applicable to your Holley model.
