In order for proper fuel deliver there must be a proper fuel level in the carburetor fuel bowl. Whether it is a 1, 2 or 4bbl carburetor.
f the level is too low there will be a lag in take off or lack of power as the RPM increases. Sometimes there will be surging at cruising speeds.
If the float level is too high there will be flooding or fuel spilling over into the venturi of the carburetor unmetered.
For this tech tip we will cover the Holley 2 and 4bbl carbs with the sight screw on the fuel bowl, like the model 2300, 4010, 4011, 4150, 4160, 4180, 4500. All of these have a brass sight screw on the side of the fuel bowl. In the case if the 2bbl there is only 1 fuel bowl therefore only 1 sight screw. For the 4bbl carbs there are 2 sight screws.
Start the motor and run it for 30 seconds. Turn the motor off and wait 30 seconds for the fuel pressure in the fuel bowl to stabilize. Then remove the sight screw on the side of the fuel bowl. If the fuel trickles out then you are perfect. If it pours out then the level is too high. If nothing comes out then the level is too low.
If the fuel level is too high, put the sight screw back in the fuel bowl and loosen the screw on the top of the fuel bowl and turn the nut below it clockwise 1/2 turn and tighten the screw back down. Start the motor and run for 30 seconds. Turn the motor off and wait for 30 seconds. Then remove the sight screw again to see if fuel trickles out of the hole. If not, then repeat step until it does. Each time remember to put the sight screw back in to the fuel bowl to avoid fuel spillage.
If the fuel level is too low, follow above procedure except turn the nut counterclockwise and repeat above procedure until the desired float level is achieved.