Narrative:

Cylinders were removed and sent out for inspection. Upon return; cylinders were preassembled; rocker arms had been installed. Cylinders were installed onto crankcase and rocker arms were removed one at a time to install push rods; tappet plunger assemblies; pushrod tubes and seals. Dry tappet clearance check was performed and found within limits. Engine run-up; leak check and break-in all appeared normal. After 25-hours; the oil was drained and the filter and suction screen were inspected. No contamination was noted; therefore; the rocker covers were not removed. I found upon inspection after an emergency landing; the rocker arms on the # 2 and # 3 cylinders to be improperly assembled. The # 2 cylinder had two exhaust rocker arms installed and the # 3 cylinder had two intake rocker arms. The part numbers (P/north) were hard to read on some of the rocker arms. Because the rocker arms were improperly assembled; there was contact between the pushrod and the rocker arm during operation that wore away pushrod material to the point of failure on the # 3 cylinder. The # 3 cylinder was removed and inspected. All rocker arms were replaced and damaged rods were also replaced. Dry tappet clearance [check] was redone on all cylinders. Engine run up and leak check will be completed. A test flight will also be completed.

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Original NASA ASRS Text

Title: Three months after installing repaired cylinders on a turbocharged IO-360 Lycoming engine; pilot experiences loss of # 3 cylinder and strong engine vibrations at 6;500 FT; night time VFR. Emergency declared and pilot notes that ATC's help and support was wonderful in getting the Mooney M20F aircraft to an alternate airport. An exhaust push rod had failed due to an intake rocker arm had been installed at the # 3 cylinder exhaust rocker arm position.

Narrative: Cylinders were removed and sent out for inspection. Upon return; cylinders were preassembled; rocker arms had been installed. Cylinders were installed onto crankcase and rocker arms were removed one at a time to install push rods; tappet plunger assemblies; pushrod tubes and seals. Dry Tappet Clearance Check was performed and found within limits. Engine run-up; Leak Check and Break-in all appeared normal. After 25-hours; the oil was drained and the filter and suction screen were inspected. No contamination was noted; therefore; the rocker covers were not removed. I found upon inspection after an emergency landing; the rocker arms on the # 2 and # 3 cylinders to be improperly assembled. The # 2 cylinder had two exhaust rocker arms installed and the # 3 cylinder had two intake rocker arms. The Part Numbers (P/N) were hard to read on some of the rocker arms. Because the rocker arms were improperly assembled; there was contact between the pushrod and the rocker arm during operation that wore away pushrod material to the point of failure on the # 3 cylinder. The # 3 cylinder was removed and inspected. All rocker arms were replaced and damaged rods were also replaced. Dry Tappet Clearance [Check] was redone on all cylinders. Engine run up and Leak Check will be completed. A test flight will also be completed.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.