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AERONCA Engine Handbook Table of Contents Previous Section Next Section Index Home
PART II - OPERATION SECTION 6 - TOP CYLINDER LUBRICATION A - PURPOSE The chief purpose of top cylinder lubrication is to prevent excessive wear of the various contact surfaces at the upper end of the cylinder. These include the cylinder walls, rings, pistons, valve guides and stems. Many new engines are "Run In" at low speed with a lubricant mixed with the gasoline by some method such as described below. That lubricant prevents the formation of excessive friction and heat which takes place between any two moving parts that are new during the "wearing in" process. It is very important that the two contact surfaces be more or less "lapped" together so that they will run with the least amount of friction and it is for this reason that the use of a top cylinder lubricant is highly desirable. The continued use of a top cylinder lubricant is advisable after the engine has been "run in" due to the fact that this lubricant will oil all of the moving surfaces and so keep the friction down to a minimum, thus greatly prolonging the life of the engine. Tests have shown that it is possible to reduce the valve stem temperatures by as much as 250 in some engines through the use of a top cylinder lubricant. Tests have also shown that the greatest wear on the cylinder walls occurs during the "warming up" period and it has been found that the use of a top cylinder lubricant will reduce this wear to a negligible amount by providing lubrication during the "warming up" period. B - METHOD There have been many methods devised for lubricating the upper end of the cylinder, particularly the valve guides and stems, of internal combustion engines. Among these many be mentioned top oilers which will depend upon the vacuum in the intake system for their operation and which must be refilled from time to time as the special lubricant is used up; direct lubrication of the valve guides and stems which is very tedious in that they must be oiled quite often in order to do any good; and last, the use of a lubricant directly in the gasoline which also thoroughly lubricates the entire carburetor system. This last method is advocated by a number of oil companies in that they are mixing a special oil directly into their automobile gasoline and advertising it as "lubricated" gasoline. C - USE IN AERONCA ENGINES The use of a top cylinder lubricant in the AERONCA engine is desirable. It lubricates the valve guides and stems besides keeping the carburetor intake system, rings, and pistons in good condition. It also decreases the carbon formation in the cylinder head which is very desirable. It is most important that the top oil used in AERONCA engines should not contain animal fat, vegetable fats, Oleic acid or similar substances in any form. These requirements positively preclude the use of all lubricants containing acid, alkali or sulfur, which, instead of protecting, would inevitably pit or etch the many bearings used throughout the engine. Top cylinder lubricants are usually sold under two classifications - the first, known as a top oil concentrate is a special neutral mineral oil which, through refining, has acquired superior oiling qualities which many oils lack. This makes this type of oil highly desirable for top cylinder lubrication. The second is known as a top oil and is a diluted form of the top oil concentrate. The diluting oil is usually a very light viscosity cylinder oil and the ratio of concentrate to cylinder oil may vary from 1:2 to 1:6 or more. The addition of this light cylinder oil does not appear to have any bad effects on the engine, such as increased carbon formation, etc., but it is necessary to use more of the top oil per gallon of gasoline than the special concentrate oil. It will be found more convenient to use the concentrated form for the top cylinder lubrication of AERONCA engines as a much smaller quantity of the oil is required and it can be carried in a small can.
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