All small horsepower engines, with the exception of the Wraith, were fitted with oil pumps in which both gears rotated about axles integral with the gear. The idler or driven gear rotates about two relatively short stubs which can wear rapidly. Later pumps, and also that fitted to the Phantom 2, were fitted with an idler gear that rotated about a fixed spindle. The gear was bored out and fitted with a bronze bush, and with the fixed spindle this gave an extended life. The same design was continued after the war with the Bentley Mark 6 engine.
The high capacity pump that was designed by Fiennes Restoration prior to its demise, and is now outsourced for manufacture, incorporates the modified driven gear rotating on a fixed spindle to give a longer life to the pump. All replacement gears are also manufactured to the modified specification.
If replacement gears are required for an original high capacity pump both a driven gear and its fixed spindle will be required. As the bush in the body that carried the original gear will have a worn internal diameter a new bush will be required to which the spindle can be fitted. The spindle is hardened on its working surface. However one end is left soft. This end is fitted in the pump body, and it should be drilled transversely and the drilled hole taper reamed for a taper pin to be fitted. This will prevent the spindle from moving in service.