As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT ENGINE DEVELOPED OIL LEAK IN-FLIGHT. RETURNED TO BASE WITH NO PROBLEMS. FOUND HOLE IN NR 3 CYLINDER VALVE COVER. REMOVED VALVE COVER AND FOUND BOTH ROCKER SHAFT RETAINING BOLTS BROKEN. TIME ON PARTS SINCE ASSEMBLY AFTER REPAIR, 96.6 HOURS.