As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE RIGHT ENGINE BEGAN TO RUN ROUGH AND LOST OIL PRESSURE. THE PILOT SECURED THE ENGINE AND MADE A SAFE SINGLE-ENGINE LANDING. AN INVESTIGATION REVEALED A CRACK IN THE PISTON. THIS CRACK STARTED FROM THE OIL CONTROL RING LANDING THROUGH THE CENTER OF THE PISTON AND A HOLE WAS NOTED IN THE TOP OF THE PISTON. NO OVERHEATING OR ABNORMAL WEAR WAS NOTED. SUBMITTER STATED CAUSE UNKNOWN.