Fig. 101.-Sectional View of Automobile Engine Cylinder, Showing Defects that Will Reduce Engine Efficiency. packings form an effective seal against leakage of water and positive retention means for keeping the explosion pressure in th cylinder. The great advantage of the detachable head is that it permits very easy inspection of the piston tops and combustion chamb interiors which can only be done with cylinders of the L, or T, form by removing the cylinder from the engine base. Two forms of removable cylinder heads are shown at Fig. 104. They are similar in design and utilize the same form of gasket, the only difference being that the type shown at A, serves two cylinders while the one outlined at B, covers the four cylinders. The construction at A, is used on the Oakland ear while that at B, is found on the Ford, Metz, Regal, Carterear, Maxwell, Oakland and several others. The cylinder heads are securely held by substantial retention bolts and if these are properly tightened and the gasket is in good condition there is not likely to be any loss in pressure due to leak Fig. 102.-Cylinder of Cadillac Four Cylinder age. One of the most important things to look for when the cylinder has been removed or the cylinder head taken off, if that method of construction is followed, is carbon deposits. These accumulate at the various points indicated at Fig. 105, namely the piston top, valves, around the spark plug and at several points in the combustion chamber. ties Carbon Deposits, Their Cause and Prevention. Most authoriagree that carbon is the result of imperfect combustion of the fuel and air mixture as well as the use of lubricating oils of improper flash point. Lubricating oils that work by the piston rings may become decomposed by the great heat in the combustion. chamber but at the same time one cannot blame the lubricating oil for all of the carbon deposits. There is little reason to suspect that pure petroleum oil of proper body will deposit excessive amounts of carbon, though if the oil contains a resinous or animal fat filler there would be much carbon left in the interior of the combustion chamber. Fuel mixtures that are too rich in gasoline also produce these undesirable accumulations. A very interesting chemical analysis of a sample of carbon seraped from the interior of a motor vehicle engine shows that ordinarily the lubricant is not as much to blame as is commonly supposed. The analysis was as follows: It is extremely probable that the above could be divided into two general classes, these being approximately 32.2% oil and combustible matter and a much larger proportion or 67.8% of earthy matter. The presence of such a large percentage of earthy matter is undoubtedly due to the impurities in the air, such as road dust which has been sucked in through the carburetor. The fact that over 17% of the matter which is combustible was not of an oily nature lends strong support to this view, while the ratios of the constituents of the incombustible material to one another is very nearly what would be expected in débris from ordinary macadam roads. If one assumes that half of the combustible matter, not of oily derivation, comes from the road dust and that one-fifth of the oxide of iron also arises from this source, the approximate composition of this cylinder deposit may be expressed as follows: It will be evident that fully 50% of this deposit can be attributed to the ordinary dust of the highway and not to excessive fuel or an impure grade of lubricating oil. While it is imperative to H Fig. 104. Showing Utility of Detachable Cylinder Heads and How They Make for Superior Accessibility of Valves and Combustion Chambers. use as little gasoline in the mixture as possible and to supply only the proper quantities of high grade lubricating oil, it will be evident that even if these precautions were carefully observed |