Spark Ignition Aircraft Engine Endurance Test of Aviation ... - FAA

The camshaft lobes, shown in figure 53, experienced normal wear.
Figure 53. Posttest Camshaft Lobes
The crankcase main bearing bores were all within the manufacturer’s new limit specifications at
the end of the test. The crankcase halves are shown in figure 54. There was minimal varnish or
sludge buildup.
Figure 54. Posttest Crankcase Halves
The piston pin bores were within the manufacturer’s new limit specifications at the end of the
test, and the piston skirt measurements were within the manufacturer’s service limit
specifications. The top, middle, and bottom piston ring side clearances were all within the
manufacturer’s new limit specifications at the end of the test. All the piston faces showed light
deposits, and all piston rings moved freely. Piston skirts displayed more discoloration than is
normally seen with leaded fuels and slight scuffing. There was also some scuffing at the side of
the piston above the top compression ring (see figures 55 through 57).
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