As a result of this scenario, Lycoming has for many years recommended new cylinders when engines are overhauled. To practice what they preach, Lycoming uses new cylinders on all engines shipped from the factory at Williamsport, PA, including factory overhauls. It is less expensive to install new cylinders during the overhaul as compared to having the engine torn down once or twice for cylinder replacement before it reaches the recommended TBO as an overhauled engine, says Lycoming. The added reliability must also be considered.
Essentially, Teledyne Continental Motors takes the same view of cylinders, although their approach has been more liberal in the past, and it is only in the last couple of years that they have gone to using all new cylinders on factory rebuilt engines.
Terry Horton, sales and service representative for TCM, says that for a number of years, Continental supplied reworked cylinders with channel-chromed surfaces. He says that the company eventually learned of Cermicrome®, and because there were less break-in problems associated with Cermicrome (the ceramic particles aid in the break-in process), Continental eventually abandoned the channel-chrome process altogether.
Horton explains that a few years ago, the company began to see a marked increase in the number of cracked cylinder heads. Because of this, they made the decision to discontinue the use of reworked cylinders and use only new. "We found that the head was just becoming too much of a problem. All of our warranty claims were on cracked cylinder heads. It was becoming apparent that it really wasn't worth it to recondition the bore and still have a bad head. Some of these cylinders have been around for a long time, and we had no way of knowing how much time was on them."
Horton says another factor that contributed to Continental going to the exclusive use of new nitrided cylinders was the company had invested heavily in new manufacturing processes and equipment which had lowered the cost of a new cylinder assembly. Because of this it just didn't make economic sense anymore to use refurbished cylinders. The little savings realized from refurbishing the cylinders just wasn't worth the problems that existed with the cylinder heads.
He explains that TCM still keeps open an option for Cermicrome cylinder coating for customers who desire chromed cylinders. "For roughly an additional $100 per cylinder, we will take new cylinders and have them Cermicromed. Channel-chrome is no longer an option."
Non-OEM New Cylinders Offer "Improvements."
Until recently, the only option you had if you wanted to purchase a new cylinder was to go directly to the engine manufacturer. Aircraft cylinders are a very complex part to manufacture; intricate detail, complex curves, exotic materials, and precise heat treating make it a very expensive part to manufacture as well. So up until now, aftermarket manufacturers have shied away from making replacement cylinders.
Superior Air Parts of Addison, TX, entered the market in 1993 with a line of cylinders it calls its Millennium® Series cylinder. The all-new cylinder was the first non-OEM aftermarket replacement cylinder available. Its original cylinders were replacement cylinders for the Lycoming O-235 and TCM O-200 engines. Since then, Superior has widely expanded the line of cylinders — recently introducing replacement cylinders for Continental A-65, 470, and the 520 engine line.
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