TM10-3930-660-34 16-21.PISTON PUMP - REPAIR (Cont’d) a.  If removed,  install locating pin (12) in valve block (3). NOTE The side of the wafer plate with the locating pin groove must face the valve block. b.  Assemble wafer plate (11) over bearing race (48) and plate groove over locating pin (12). CAUTION Wafer plate (11) must be flat against valve block face.  Check to make sure it does not rock back and forth.  If rocking motion occurs,  make sure locating pin (12) is bottomed out in the valve block (3).Wafer plate rocking will induce high stress conditions and cause fractures in the wafer plate. c.  Place valve block (3) on its side.  Install piston rod (8) into valve block (3) and attach retaining ring (47). d.  Install new O-ring (46) in the piston rod (8) O-ring groove. CAUTION Be careful not to allow the piston to drop from piston rod as this could damage the piston. e.  Install piston (7) over piston rod (8). f.  Assemble valve block (3) to housing (6) with six screws (9). g.  Cross tighten screws (9) to bring valve block and housing evenly together against gasket (10). Torque screws (9) to 60-70 lb.  ft. 16-142