The carburetor installed on a stock 1979 Ford F-350 is a Holley 0-90470. This carburetor belongs to the Avenger series and has an air flow rating of 470 CFM (cubic feet per minute). It's a four-barrel carburetor with vacuum secondaries, electric choke and a square-bore mounting base plate. Tuning a four-barrel carb is similar to tuning a two-barrel, but will require identical tuning steps on the secondary components along with the primaries.
Tools Used: Screwdriver, Wrench set, Socket wrench set, Pliers, Vacuum gauge
Tune Holley Carburetor
Place the truck on a level surface, pop the hood and peer into the fuel level sight windows on both the primary and secondary fuel bowl (on the front and rear of the choke tower, respectively).
Verify that the fuel rests at the base of the sight window. If fuel is above or below the base of the window while the truck is rocked slightly from side to side, float adjustment will be required.
Start the engine and adjust the float down by screwing the adjustment nut (on the top of the fuel bowl) clockwise to lower the fuel level within the bowl. Turn it counterclockwise to raise the float as necessary until the fuel rests at the base of the sight window.
Tighten the float valve adjustment screw, holding the adjustment nut stationary. Perform this adjustment process on both bowls.
Idle the engine and locate the screw on each side of the primary metering block. This is the idle mixture screw and will tune the vacuum on the carburetor, affecting the idle conditions. Attach a vacuum gauge to the intake manifold service port.
Adjust the idle mixture screws equally until maximum vacuum is reached. Complete this process on the secondary metering block idle mixture screws as well.
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