As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON REMOVAL OF THE OIL SUMP TO REPLACE A LEAKING GASKET, FOUND 2 CASE HALF BOLTS AND ASSOCIATED HARDWARE (NUTS AND WASHERS) HAD COME OUT AND WERE LAYING IN THE SUMP. INSPECTION OF THE CASE HALF BOLT HOLES SHOWED NO SIGN OF FORGING ON THESE 2 BOLTS. IT IS THEORIZED THEY WERE INSTALLED BY HAND DURING ENGINE ASSEMBLY, BUT FAILED TO BE TORQUED. THUS, THEY LOOSENED AND FELL INTO THE SUMP.