If you fly a “big bore” Continental engines you have a problems waiting inside. These engines are notorious for lifter failure. This is a problem due to “spalling.” So, what is spalling and what causes it on metal lifters.
Spalling is defined as:
“Metal spalling is a process of metallic surface failure in which the metal is broken down into small flakes (spalls) from a larger solid body. This process occurs for many reasons, such as when another material impacts it at a high-speed resulting in chipping the material, or due to corrosion, weathering, cavitation, or excessive rolling pressure.”
One thing to mention is that spalling can occurring between two different types of metal. If you have one type of metal that is slightly harder and is also very firm, then that will affect the opposing metal. In the case of spalling involving lifters the camshaft is a harder material than the lifter face. In other words, you have a hard metal (camshaft) striking a stable lifter with that lifter getting “banged” by the camshaft.
So, what does a lifter do for those who do not know. They are the intermediary between the valve and the camshaft. They are the device that takes the “BANG” when the camshaft comes around and slams the lifter to push the valve open. In the big bore Continental engines, they do not have what I consider to be a satisfactory lubrication. In other words, since they lay horizontally in the engine, they will have oil that may not stay on them while the engine sits still. Many mechanics think it is an oil problem but these lifters in these big engines have a problem not considering any lubrication.
One other thing that is out in the “rumor mill” is that these lifters are made in Mexico or some other “out of the United States” country. This, however, is not the problem. These lifters as previously stated have always had a problem.
So, what do you do to solve the problems. As the guys at Air Impressions say you must have a mechanic that is “proactive” to catching and resolving the problem. You must set up an inspection procedure based on engine time. If you can catch the spalling early you save the camshaft. If you save the camshaft you don’t have to pull the engine and spend a fortune putting in a camshaft. To install a camshaft is expensive. To install lifters is reasonable.
They are pretty easy to get to and they just “pop” out. So, the bottom line, is to set up a time on the engine to examine the lifters.
We are of the mindset to examine them at 400 hours. In fact, if you buy a plane that has more than 400 hours on the engine(s) you should have the lifter exam done at the pre-buy. Most mechanics are NOT examining the lifters. If you have an aircraft coming up on 400 hours like 300 or 350 why don’t you have the mechanic take a look early?
Have we at AST had lifter problems? Yes, on an engine with 1100 hours but we caught it early. This is “easy-peezy” to get them looked at and checked.
Remember an ounce of prevention is worth a pound of cure. Start early and inspect them. We are showing you a set of lifters with the good, the bad, the really bad and in between.