Whistling holley 1920

You can weld or rivit that hole closed, as it is not factory and probably where the whistle is coming from.
People do that to a carb because the cam they used needs more air to idle higher and stay running.

You might use a small screw and nut if it will clear everything, but I would'nt use that method unless I peened it down or locktighted it so there would be zero chance of it coming loose and going into the motor.

My original carb had strange issue's when I first got the car and it took awhile to find out someone had drilled two holes from the outside of the carb base to under the butterflies, basically for the same reason but UNFILTERED air???
Some peoples kids, ugh.