One of the most crucial, yet overlooked adjustments in a Holley four-barrel carburetor is the float. Adjusting the float and fuel level on a Holley four-barrel carburetor is easy if you follow these basic steps. By Taylor Vlahos, DS Media First, it's important to know how the fuel float system operates.tep 5: Fuel Level Is Too High If fuel is pouring out of the sight plug then the fuel level is set too high, and the float must be lowered in the fuel bowl. a) Begin by lowering the fuel level in the fuel bowl to bring down the float.