How to prevent cam and lifter wear

Reader Dave Fletcher recently sent an email concerning the failure of the camshaft in his Lycoming IO-360 engine. He was concerned about pre-oilers, Ney Nozzles, CamGuard and other oil additives.

This is a subject that both engines expert Paul McBride and I have addressed before, but I thought I would try to add a little background to the debate.

To understand the problem with Lycoming camshaft wear, one needs to look at the physical layout of the Lycoming engine. The camshaft is on top of the crankshaft as opposed to Continental engines with the camshaft below the crank. When most aircraft sit idle, air enters the cowl openings at the top of the engine, so the top is affected by ambient air temperatures before the rest of the engine. During the day, the crankcase is warmed up and filled with warm humid air. In the evening and at night, the engine cools down and moisture collects in the oil.

As more and more water collects, the air in the crankcase becomes more humid, so in the evenings the cam cools faster than the rest of the crankcase. Once the cam cools below the dew point of the air in the crankcase, moisture drops out on the cam. Over time, this water causes rust to form on the cam and lifter surface. When the engine is finally started, the rust acts like a lapping compound to start wear on these surfaces. It is important to realize that the majority of cam and lifter wear starts in the first revolution of the cam.

The problem with pre-oilers is that oil comes out the cam bearings and lifter barrels, but no oil gets onto the cam and lifter interface for that first revolution. Even the Ney Nozzles promise oil to the lifter interface within one revolution. The pre-oilers get oil to all bearing surfaces quicker, but have little or no effect on that critical first revolution.

So do additives help prevent cam and lifter wear? They may help. The reports on CamGuard vary from a marginal effect to a complete cure for the problem. However, there are a host of other additives that have no beneficial effect and are a complete waste of money, and many of them are not FAA approved.

So what is the answer to preventing cam and lifter wear? The biggest thing you need to do is have dry oil. To do that you need to make sure your oil temperature is high enough to boil the water that is condensed into your oil. To do this, I recommend that all plane owners remove their oil sending unit, put it in a container with oil, water or even chicken soup, and place the container on a heat source. With a good thermometer, make sure the container is heated to 180°F. Then check your gauge. I recommend making a paint mark on the gauge so you can easily reference where 180° is when flying.

Now go fly and check your gauge. If after a half hour or so your oil temperature is not up to 180°, take steps to raise it up. If it is well over 200° during a level cruise, you may need to lower it. The reason for this is that as oil goes through your engine, the highest instantaneous oil temperature is usually about 50° higher than oil entering the engine temperature. At 180° the oil will see 230° in the engine, which will boil off the moisture. If you operate at 230° during level flight, the oil is getting to 280°, which can lead to problems.

So what is the bottom line? I have found that Lycoming engines that operate with a “true” oil temp of 180-200° and are flown regularly almost never have cam and lifter problems. If you live in a humid climate and operate with an oil temp well below 160° and do not fly regularly, then the chances are pretty good that you may have a problem. If you are not going to fly for a period of time, like over the winter, change the oil and add a quart of preservative oil that meets Mil-C-6529C Type II specification.

Pre-oilers, additives, brand and grade of oil, etc., fall into the great gray area of maybe they will work or maybe not, but why depend on them when you have an almost sure thing.

Comments

  1. Thank you so much for a very comprehensive article. I have a Partenavia with two of IO-360′s, it only does about 350 hours a year, with long breaks, it is used for Multi-engine and IF training, it was losing power in both engines, had them removed and overhauled, and the cam shafts were so worn, that the engineer commented that it was near failure time. Now both engines are developing so much power it is like a “newy”.
    I am now in the process of having our engineer carry out your suggestion.

    Again thank you very much

  2. Do you think that those forced air-dryer units that pump desicated air through the crankcase have any value?

  3. Matthew Lawrence says:

    Ben, After years of renting, and a two-year flying hiatus, I am seriously moving toward aircraft ownership, for knockabout flying, and perhaps an extended venture.

    Thanks for your article on camshaft wear and moisture. Your straightforward solution is regular exercise. “I have found that Lycoming engines that operate with a ‘true’ oil temp of 180-200° and are flown regularly almost never have cam and lifter problems.”

    How often is ‘flown regularly’ for dry oil, given three senerios; a humid stretch, a dry month, and weekly shifting periods of high/low humidity? (I live in New England.)

    I know that for me, aircraft use will fall off some after the first blush of ownership has settled down.

  4. Fritz Katz says:

    Fine piece but
    1) I assume you meant to say “oil TEMPERATURE sending unit” for those readers barely familiar with engines who without that clue might be looking for pumps and capillaries
    and
    2) did you really encourage people to put a pot of OIL on a stove and fire it up to test temps…instead of JUST water or soup?
    Keep your lawyer on speed dial after that one.
    PS I use CamGuard in my classic cars also. Expensive shit but worth it

    • Neil Fogle says:

      Assuming that you are operating your engines at the proper temperature and when you shut them down there is no moisture in the engine. The solution is to prevent moisture from entering the engine or make sure the engine never goes below the dew point.

      You can prevent moisture from entering the engine by covering the crancase vent or making the air entering the vent pass through a dessicant. The other solution would be to have a very low temp heating device on the engine to assure that the temperature never goes below the dew point. 100 degrees F should do tne trick. Cam Guard is just good insurance.

  5. A guy I know runs a plastic tube down the dipstick tube, and the other end is attached to a fish tank pump. It draws air through a bag of desiccant (silica) to remove moisture from the air in the crankcase. Once a month he puts the silica in the oven to dry it back out.

    • Ray Toews says:

      I have to disagree with the expert advice. It is not corrosion from repeated condensation. If this was the case our fuel tanks would be filled with water. A small confined space like the crankcase will hardly have enough air to cause tht much condensation.
      I believe the problem with Lycoming is precisely the location of the cam, above the crank.
      Crank your engine for 10 seconds before adding fuel and the cam wear problem will go away.

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