Every part that goes into a flight engine has its own part number in my conversion manual. The first two digits are the group chapter in the book. For example, lets look at the simple oil fill cap, #1905.
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Because it’s first two digits are 1-9, it is in chapter #19, the valve cover group. The manual explains how we set up engine valve covers, and how they have the crankcase vents on one side and the oil fill on the other. There are pictures and descriptions. The locations on the valve covers have very little internal oil spray, Oil can be added without removing the cowl, and you can also take the cap off and look at the #1 rocker and see which stroke the engine is on without the need to remove a spark plug. The locations on the covers have been evolved over time to make sure it clears all the cowls, etc. A lot of thought goes into installation details that is not readily apparent at first glance.
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Above, six parts go in a yellow powder coated #1905 oil cap. L-R The blasted and coated cap, brass spring disc, main gasket, central washer, inner gasket and AN rivet. We drill new ones apart, to have them powder coated yellow, the traditional oil filler cap color on US certified engines. I rivet them back together when done. Its elaborate, but these caps are included in our powder coated valve cover kits. These are the covers you see on most of the engines at the colleges. If you are a good welder, you could build your own copy of them, and paint them and use the stock oil cap and save some money, but most people pick a color and have us send a set to them.
