What was found
(CAN) ENGINE INDICATING SYS & PARAMETERS WERE OP NORMALLY.AT 164.1 HRS OF OP, A CYLINDER DIFFERENTIAL CHECK WAS CARRIED OUT. ALL CYLINDERS WERE FOUND TO BE IN 60/80 RANGE. A/C CONTINUED TO FLY & AT 260.6 HRS OF OP, A 2ND DIFFERENTIAL CHECK SHOWED READINGS OF LOW 50'S WITH ONE CYLINDER 24/80. 2 CYLINDERS SHOWED EXHAUST VALVE LEAKS. TCM WAS CONTACTED & ALL CYLINDERS WERE REMOED & SENT TO A REPAIR STATION FOR INVESTIGATION. THOSE CYLINDERS WERE REPAIRED & INSTALLED. A/C WAS GROUND RUN & TEST FLOWN, PRODUCING ADEQUATE POWER IN ALL FLT CONDITIONS.