Basically there are 4 types of oil pumps for Spittys:
- MKI & MKII type
- MKIII type
- MKIV and Early 1500 type
- Late 1500 type
All these pumps are basically inter-changeable, i.e. you can fit a MKI pump to a 1500 and vice versa, except in the case of the MKI pump, the gauze in the sump will need to be removed. The best pump is the late 1500 type as it is more efficient. The least efficient is the MKI type with the others somewhere in between.
The actual differences between the pumps are as follows:
- MKI & MKII types are both all iron construction with a very basic pickup with the inner and outer rotors being 1" long.
- MKIII type is the same as the MKI & MKII type, but with aluminium pickup and with more efficient ducting in the casting.
- MKIV and early 1500 types are the same as the MKIII type, but with gauze on the end of the pickup.
- The late 1500 type has a completely different body and the inner and outer rotors are longer — being 1 1/4". The pick up is a different design, a vastly better pump.
Remember this: a tired motor with a good oil pump will last a long time, but a good motor with a worn out oil pump will not last a long time.