What was found
PILOT REPORTS (GRINDING) SOUND WHEN PROPELLER IS SPUN BY HAND. THE ENGINE WAS SPLIT AT THE (C) FLANGE WHERE DEBRIS WAS NOTED AT THE 6 O'CLOCK AREA BETWEEN THE COMPRESSOR TURBINE BLADES AND SHROUD SEGMENTS. AFTER REMOVAL OF THE CT DISK, IT WAS NOTED THAT FOUR BOLTS HOLDING THE INNER EXIT DUCT TO THE ENGINE WERE MISSING. THE DEBRIS WERE THE REMAINS OF THE FOUR BOLTS. SAFETY WIRE WAS NOT PRESENT IN THE REMAINING FOUR BOLTS. 370 HOURS SINCE ENGINE O/H.