What was found
DURING CLIMB, WHEN CLEARED INS WAYPOINT AND SELECTING INS MDU, CDI ON C/A AND F/O HSI WOULD NOT CENTER X WHEN CLEARED VOR AND SELECTING ON INS MDU, HSI SHOWED ABOUT 30 DEGREE DIFFERENCE IN UPDATE. EXCESSIVE DIFFERENCE IN DRIFT ON ARRIVAL . 23400 FUEL DUMPED. AC RETURNED. INS CHECKED OUT IAW 34-41-00. HSI/ADI INTERFACE CHECKED ALL INDICATION IS NORMAL W/OUT REMARKS.