A swirl pot allows air to escape from the cooling system during normal operation. If your radiator fill cap is not the highest point in your cooling system, you need a swirl pot.
This aluminum swirl pot gets installed by running the outlet (discharge) from the engine block into the upper (side) inlet on the pot. Coolant swirls around the inside of the pot as it flows to the bottom, allowing air bubbles to break up and escape via the top vent tube. Coolant is drawn out the bottom outlet, through the radiator, and back to the water pump suction side. The center vent can be connected to the radiator air bleed or catch tank. The cooling system should be filled until the swirl pot is about 2/3 full. This ensures adequate space for the coolant to de-aerate, while also providing a sufficient volume of coolant in the swirl pot to prevent pump cavitation.
Body measures 195mm (7 5/8") tall x 65mm (2 9/16") OD. Inlet and outlet both accept 32mm (1 1/4") ID hose. Air vent fitting accepts 8mm (5/16") rubber hose.