Thursday, December 27, 2012

Pulling the Prop Through

                  Note the factory is quoted verbatim here per Lycoming SL 180B: "Pulling engines through by hand when the aircraft is not run or flown for a week or so is not recommended. Pulling the engine through by hand prior to start or to minimize rust and corrosion does more harm than good. The cylinder walls, piston, rings, cam and cam followers only receive splash and vapor lubrication. When the prop is pulled through by hand, the rings wipe oil from cylinder walls."

                  "The cam load created by the valve train wipes oil off the cam and followers. After two or three times of pulling the engine through by hand without engine starts, the cylinders, cam and followers are left without a proper oil film. Starting engines without proper lubrication can cause scuffing and scoring of parts resulting in excessive wear."

                             Note that pulling the prop through prior to starting is a different story. Here you will be starting the engine and it will be immediately receiving lubrication. Also, pulling the prop through in this situation will check for the condition of the valves i.e. you are feeling for any flat spots in the compression, or other untoward signs of abnormal prop feel as the pistons are cycled.
             Lycoming SL 180B


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