Air deflectors which are part of the thermostat system. These are located at the base of the fan shroud and are actuated by the thermostat bellows /check rod. When the engine is cold, the flaps are closed reducing the amount of cooling air that reaches the cylinders and heads. As the engine warms up, the bellows expand causing the check rod to open the flaps and allowing a full amount of cooling air to blow across the cylinders and heads. These are often removed.