As far as to not ever drilling plates, not true, holley drilled and reamed .078-.080 holes on all 6 plates on factory 6bbl 440 setups, 383 holley carbs had holes. the air has to come from somewhere for it to idle with the plates closed. I doubt a 400 inch engine could idle on 4 idle circuits with all 4 blades closed, most have the rear blades cracked by the set screw for idle air. If you have an adjustable air bypass, different story.