This oversize water pump pulley is stock on late Mini 1000s, but will fit all Classic Mini models using suitably-sized head. 4.75" diameter.

Reduction of cavitation in the water jacket is achieved by using a large diameter water pump pulley. Originally fitted to the Cooper S and reintroduced on the A-Plus engines, this oversize water pump pulley is stock on late model cars but will fit all models. Designed to reduce the horsepower drain and slow the water moving through the radiator to allow it time to cool - very important for the higher RPMs we run today. Use of a high capacity water pump also helps to reduce cavitation in the water jacket, particularly at high RPM, as well as circulating a greater volume of coolant. It is necessary to check clearance between the large pulley and the head; if a lot of material has been machined from the head face (the head has been surfaced too many times) it may foul the pulley.

Small bore engines with 12G940 heads can't use this pulley. Instead see CAM116.