As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED THAT ON DOWNWIND IN THE TRAFFIC PATTERN AT THE DESTINATION AIRPORT, HEARD A LOUD "POP", AND AND EXPERIENCED A POWER LOSS ON LT ENGINE. NOTICED OIL AND SMOKE COMING OUT OF LT ENGINE COWL. SHUTDOWN ENGINE AND FEATHERED PROPELLER IAW THE ENGINE FAILURE CHECKLIST AND LANDED NORMALLY. VISUAL INSPECTION OF ENGINE REVEALED A QUARTER SIZED HOLE IN THE LT ENGINE CASE NEAR THE FWD ENGINE HOIST RING.