As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED LEFT ENGINE STARTED VIBRATING IN FLIGHT, WHEN MANIFOLD PRESSURE WENT TO AMBIENT. THE ENGINE WAS SHUT DOWN IN FLIGHT AND WOULD NOT RESTART. UPON INITIAL INSPECTION THE CRANK CASE WAS FOUND TO BE PENETRATED AT THE REAR OF THE ENGINE IN THE VICINITY OF THE NR 1 CYLINDER. THE ENGINE IS BEING REPLACED, FURTHER DETAILS WILL BE PROVIDED UPON ENGINE TEAR-DOWN INVESTIGATION.