Is that a Buick motor or an SBC (cant tell from here), with it being on the passenger side. At any rate, an AC DELCO or Carter pump at the motor parts should only be about 15-20.00 Change it for peace of mind. Some motors us a "cup" that bolts onto the cam shaft with a push rod to the pump. That could be loose, the arm pin on the pump can be loose or even the pump itself may be a tad loose. Try tightening it? Just some random thoughts... ws