As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENGINE INSPECTION, IT WAS NOTED THAT THE NUMBER ONE MAIN BEARING DOWEL WAS INSTALLED BACKWARDS WITH IN THE CRANKCASE BEARING DOWEL BORE. THE IMPROPERLY INSTALLED DOWEL PREVENTED THE NEW BEARING FROM FULLY SEATING WITHIN THE CRANKCASE BORE.