What was found
(CAN) ON TAKEOFF PILOT FELT SLIGHT VIBRATION THROUGH RUDDER PEDALS. AFTER GETTING TO HIS CRUISE LEVEL THE VIBRATION GOT WORSE. HE RETURNED TO THE AIRPORT, AC WAS BROUGHT INTO MAINT SHOP AND COWLING WAS REMOVED. COMPRESSION TEST WAS COMPLETED AND IT WAS FOUND THAT NR3 CYL NO COMPRESSION. CYL WAS REMOVED FROM ENGINE. FOUND THAT THERE WAS A HOLE BURNED UNDER THE EXHAUST VALVE SEAT AND THERE WAS A PART OF THE EXHAUST VALVE MISSING. RECORDS INDICATE THAT AT ENGINE OVERHAUL THE EXHAUST VALVES AND SEATS WERE REPLACED. AME WONDERS IF WHEN THEY CHANGED THE SEAT THAT THEY MAY HAVE CRACKED THE CYL ALLOWING THE EXHAUST GASES TO BURN THROUGH THE CYL UNDER THE SEAT. (TC NR 20080428002)