As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PROPELLER AND ENGINE PULSE CAVITATION IN FLIGHT. SIGNIFICANT OIL LEAK ON GROUND. HAD 19 INCHES MANIFOLD PRESSURE, 2100 RPM WHEN SLOWLY ADVANCING RPM. AIRCRAFT GROUNDED. MECHANIC PERFORMED A COMPRESSION CHECK ON THE ENGINE AND FOUND THE NR 2 CYLINDER HAD AN ACCEPTABLE COMPRESSION OF 70/80. FURTHER INSPECTION IAW SB388C REVEALED THAT THE EXHAUST VALVE TO GUIDE CLEARANCE WAS .029", WHICH IS BARELY UNDER THE MAXIMUM CLEARANCE (.030") ALLOWED IAW PARAGRAPH 12. CYLINDER WAS REMOVED FOR REPAIR.