Anyone ever done this to an afb?

“The solution to idle quality on "driver" vehicles (not numbers matching) is to install a conventional idle control. There is a "dimple" in the lower casting on the front drivers side (where the normal curb idle screw would be located). Drill through the dimple using a number 21 drill, and tap for a number 10 x 32 machine screw. Obtain a 10 x 32 machine screw and spring at the local hardware or auto parts store. Install the screw and spring. Screw the idle air screw all the way in, and then adjust the idle the conventional way.

If you wish to leave the adjust as the factory suggested with the idle air screw: for MOST applications, the beginning settings would be 1 turn on the idle mixture screws and 1 1/2 turns on the idle air screw.

Where these carbs are really useful is for those using big cams (low vacuum). The idle air screw, used in conjunction with the conventional idle screw is an adjustable idle bypass. Remember the holes drilled by the factory in the throttle plate on some of the performance carbs? No need to drill, as the idle air screw will do exactly the same function, and it is adjustable.”