The first step is to set the curb idle speed to between 750 and 850 RPM, once completed you can  then check ignition timing and adjust if needed.

Now setting the mixture screws, part number(s) Holley 1540 or BLP 1540-BLP (stainless). Most Holley performance carburetors have two or four mixture screws. For those with two screws,(2-corner idle)  turn the mixture screw in until you notice a drop in RPM, then back it out until you get the highest RPM you can. Stop and do the same to the other mixture screw. This is to achieve the highest RPM for the motor at idle. It may be necessary to lower idle speed once you have completed this process.
For 4-corner idle applications, you will make smaller adjustments to all four screws. After timing and base idle is set, turn the first screw in to notice a drop in rpm. Then, in quarter turn increments, adjust each mixture screw until you no longer get a positive RPM rise) result from turning the screw. After this you may need to lower your base idle speed.
If the screws do not maintain adjustment position you may need new seals you can use Holley part number 27152 or BLP 271521 (polyurethane)