Waterpump
Nissan Standard Waterpump[edit]
8 blades, fine for most applications.
GMB Waterpump[edit]
This particular pump has 6 impeller blades, not so good for high-revving RB20 as cavitates at high RPM.
Nissan N1 Waterpump[edit]
6 curved blades, slightly different casting, anti-cavitation plate behind impeller. Good for sustained high RPM. There is a slotted hole near the impeller that fits the RB26, but should be welded up and drilled round to fit any other RB, which has been done on the pump in the larger photos. This can be seen more clearly by comparing the pumps in the bottom photo. The casting under the boss is different, the stock one is cut away towards the bearing as you can see in the other pictures but the N1 has bits of the casting right up underneath and machined to fit the underside of the impeller.
Photos: Blue