As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED-ENG ROUGHNESS, WAS NOTICED ON THE LT ENGINE, TURNED ON THE AUXILIARY FUEL PUMP AND ENGINE BEGAN TO RUN BETTER BUT UNABLE TO MATCH MANIFOLD TO RT ENGINE. VISIBLE OIL FROM RT SIDE OF COWLING WAS NOTICED AND ENG WAS SHUTDOWN AND FEATHERED. MX INVESTIGATED AND FOUND THAT ON THE NR 3 CYL INTAKE VALVE COVER HAD A HOLE. AFTER REMOVING VALVE COVER IT WAS FOUND THAT BOTH RETAINER STUDS FOR THE ROCKER ARM HAD SHEARED.