CAM Lobe Failure


In 2011 I overhauled my Lycoming I/O-360 due to a cam lobe failure. During the downtime, I analyzed several years of oil analysis results to see if there were indications of when the cam started to fail. What became apparent from this analysis was the significant increase in wear rates after I moved the airplane from the mid-west to Houston, TX. This convinced me that I needed to do something to deal with the high humidity inside the engine.

I began searching for an engine dryer to purchase. The only systems I found simply took outside air, pumped it through a desiccant to dry the air, and pumped it into the crankcase of the engine. Considering the small amount of desiccant used in those systems and the high humidity levels in Houston, it was obvious those systems wouldn’t effectively dry the engine, and the desiccant would likely become saturated in a day or two.

To be effective in highly humid environments like the Gulf Coast and Houston, I came to the conclusion the system would need to seal the engine from the outside humidity, pull the moist air out of the engine, dry the air, and then pump the dry air back into the engine. Without sealing the engine and re-circulating the air from inside the engine, even large amounts of desiccant would not last very long. And, re-circulating the air would also progressively dry the air to much lower relative humidity levels than possible with a single pass system. I also concluded, the system needed to measure the relative humidity of the air from inside the engine to verify the system was actually keeping the engine dry, and to provide a means to determine when the desiccant needed to be recharged. I couldn’t find any existing system having these capabilities. As a consequence, I decided to try to build the system myself.

This seemly simple project turned into somewhat of an obsession, going through several different designs and prototypes over a couple years. (My wife has a more colorful description of this obsession.) During this time, it also became apparent the system needed to dry the entire engine, not just inside the crankcase. The exhaust system was found to be the primary source for moist outside air entering the engine. Most of the iron oxide (rust) was from the cylinder walls, and the primary source of this was moisture entering through open exhaust valves.The final system not only fulfilled the initial design objectives, but also incorporated a double feedback loop to dynamically control the system as the relative humidity of the outside air changes and as the relative humidity inside the engine changes.

Since that time, numerous friends asked me to build a system for their plane. This lead to more and more pilots seeing the system and more requests.