What was found
ENGINE L-34695-27A O/H BY TEXTRON LYC 11-8-97. INSTALLED 2-20-98. FOLLOWING TEST FLIGHT AND BREAK-IN, ACFT RELEASED FOR FLIGHT TRAINING. AT ENG SMOH 16.8 HRS ON TAKEOFF, A LOSS OF RPM AND DEGRADED CLIMB PERFORMANCE REQUIRED IMMEDIATE RETURN. SUBMITTER STATED DEFECT THAT CAUSED LOW POWER WAS 4 MISMFG'D CYLINDERS. THEY WERE NEW LYC CYLS P/N LW 12416 THAT DID NOT HAVE INTERNAL INTAKE PORTS RADIUSED. WHEN AMBIENT TEMP AND DENSITY ALTITUDE INCREASED WITH ONSET OF A HOT SUMMER DAY, CYLS CAUSED ENG TO RUN ROUGH AND LOSE POWER. FOUR NEW LYC FURNISHED CYLINDERS P/N LW 12416 WERE INSTALLED WITH PROPER RADIUS OF THE INTERNAL INTAKE PORTS. SUBSEQUENT OPER HAS BEEN SATISFACTORY WITH THE ACCUMULATION OF 98 HRS SMOH.