As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER RETARDANT DROP, THE FLIGHT CREW NOTICED OIL STREAMING DOWN THE SIDE OF THE RH RADIAL ENGINE. THE ENGINE WAS SHUT DOWN, AND AN IFE DECLARED. AIRCRAFT RETURNED TO BASE AND PERFORMED AN UNEVENTFUL LANDING. UPON INVESTIGATION, THE ROCKER ARM FOR NR 12 CYLINDER WAS FOUND TO HAVE FAILED AND PUNCTURED A HOLE THROUGH THE ROCKER COVER.