As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
NOTED OIL LEAK ON LT SIDE OF OIL SUMP. FOUND THE CRANKCASE HAD MISSING PIECES AT LT REAR OIL SUMP MOUNTING STUD. ENGINE WAS CONVERTED TO IO-360 APPROXIMATELY 100 HOURS PREVIOUSLY. A NEW OIL SUMP WAS INSTALLED AT THAT TIME. SUSPECT OIL SUMP TO CASE BOLTS WERE OVERTORQUED CAUSING A CRACK AND EVENTAULLY VIBRATION CAUSED PIECE TO DEPART CASE.