Engine vacuum draws fuel from the float bowls through the main jets into the passages of the metering blocks. The air required to emulsify the fuel in the metering block passages is drawn through these tiny air bleeds

Empowered by engine vacuum, the idle air-fuel emulsion is drawn rapidly through a multitude of small passageways in the carburetor’s metering blocks and discharged into the induction system through eight small ports in the carburetor base plate. These are known as the idle discharge ports and transfer slots.