As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, LEFT ENGINE STARTED VIBRATING. ENGINE WAS SHUT DOWN AND AIRCRAFT RETURNED TO THE AIRPORT. INSPECTION REVEALED A CRACK IN THE NR 5 CYLINDER. SINCE OVERHAULED CYLINDERS HAVE HIGH TOTAL TIME, THEY ARE MORE LIKELY TO CRACK DUE TO AGE AND STRESS. RECOMMEND USING NEW CYLINDERS AT OVERHAUL TO REDUCE RECURRENCE OF THIS PROBLEM.