The diameter of the shaft hole in the oil pump body has been increased from 9/16” to 5/8” diameter and the relief removed from the oil pump shaft.

The clearance between the shaft and body forms the oil passage through which the pump delivers oil to the valve chamber. Formerly this clearance was obtained by relieving the shaft (see A, fig 487). The clearance is now obtained by boring a larger hole in the oil pump body and using a straight shaft (See B, fig 487).

When replacing shaft in an oil pump equipped with the relieved shaft, be sure to replace it with the same type of shaft, as the present design straight shaft would not allow sufficient area for oil flow when mounted in the previous design pump body with the 9/16” shaft hole. The relieved shaft can, however, be used in the present pump with the 5/8” shaft hole.