Steel cylinder refers to the barrel, or bore / wall within the cylinder assembly. Although other RAM maintenance tips discuss the protection of the cast aluminum cylinder head assembly, it is also essential to maintain the integrity of the steel barrels, especially new steel barrels. After a major overhaul, new steel barrels need to be operated approximately fifty (50) hours to build up a deposit of varnish sufficient to offer protection against rust.
Unfortunately, right after major engine work it also seems like a good time to leave the aircraft out of service for new paint, new interior and avionics work. Anytime aircraft engines sit inactive, the steel barrels begin to rust as a natural result of the moisture in the atmosphere. This situation is even more serious in coastal areas or locations having high moisture.
The result of steel barrels rusting is pitting. With pitting comes a loss of compression and a loss of optimum power. The best method of preventing steel barrel rust is to fly the aircraft frequently. After an overhaul, try to fly the aircraft fifty (50) hours before taking it out of service for a long period of time. Subsequently, throughout the life of the engines, fly the aircraft at least once each week - long enough to reach normal operating temperatures. This is critical in order to ensure that all the moisture is vaporized.
Ground running the engines produces condensation and is not acceptable. Also remember, replacing just one cylinder still requires the same procedures and precautions as applicable to a new engine or fresh overhaul. See RAM Maintenance Tip "Engine Break-in Procedures."
Teledyne Continental Motors (CMI) has published Service Bulletin M84-10 Rev. 1, addressing this problem. It gives detailed information concerning the preservation of engines, especially during periods of inactivity. RAM recommends that all operators and mechanics read this bulletin and comply with it as applicable.
If replacing a cylinder or cylinders, ask about RAM nickel+carbide new cylinders.