Single-Function for Standard Cooling

When coolant temperature is below 160°F, check ball is held against inner seat by spring pressure. Manifold vacuum enters port "1" and is applied through port "D". This allows full manifold vacuum to distributor. Above 160°F, port "1" is blocked, and carburetor ported vacuum enters through port "2" and connects to port "D". Ported vacuum then controls spark advance. See Figure.