[Jac Mac]

The purpose of those holes is to reduce the tendency for fuel to be pulled from the main venturi under idle conditions when using a longer duration cam etc that needs a wider throttle plate setting to maintain a decent idle speed, the holes kill off airflow between the throttle plate & main venturi, many production carbs- carter etc particularly 2bbl's use the same trick. Not a really good idea when you think of the crap that can get drawn in at that point. The introduction of 'idle-ezi' by Demon & others gets around the problem and at least keeps the air cleaner.