What was found
EXHAUST VALVE BROKE ON NR 1 CYLINDER. HALF OF VALVE HEAD CAME OFF CAUSING DAMAGE TO NR 1 CYLINDER AND THEN BROKE INTO 3 PIECES. TWO PIECES LODGED IN THE MUFFLER. ONE SMALL PIECE TRAVELLED THROUGH THE INTAKE SYSTEM TO NR 4 CYLINDER WHERE IT DID DAMAGE TO THE HEAD AND PISTON, ALSO BREAKING THE LOWER SPARK PLUG. TWO SERVICEABLE CYLINDERS WERE INSTALLED ON THE ENGINE. THE ENGINE WAS RUN FOR 1.5 HOURS WITH ALL GAUGE INDICATIONS NORMAL. A COMPRESSION TEST SHOWED NORMAL READINGS OF NR 1 - 78, NR 2 - 74, NR 3 - 72, NR 4 - 79 AND THE AIRCRAFT WAS RETURNED TO SERVICE. (X)