voir, and is also directed to the camshaft bearings through a smaller manifold. The connecting rod bearings are oiled through passages drilled in the crankshaft. The oil is circulated by a gear pump driven from the crankshaft by spiral gearing, the intermediate gear serving to drive the two water pumps, one at

Fig. 220.-How Tilting Troughs, Regulated by the Throttle Control, Vary the Oil Supply for Different Engine Speeds.

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each side of the motor, by means of a cross shaft. An adjustable by-pass valve is provided so that the oil pressure may be maintained to any desired point.

Where to Look for Trouble in Lubrication Systems.-But little trouble will be experienced with the constant level splash system in which the oil is circulated by a positive pump through

passages cored in the motor base instead of long external pipes. Considerable trouble is experienced on the old style cars having a large number of individual leads running from a mechanical oiler or compression feed oiler to the various bearing points. The simple sight feed lubricator employing compression pressure to cause the oil to circulate from the tank to the manifold fittings would indicate a clogged pipe in a positive manner as the oil drip feed glass

Fig. 221.-Oiling System of Cadillac 1915 Eight Cylinder Engine.

would fill up if the pipe is constricted for any reason. In event of the failure of the oil to drop in the sight feed glasses when the adjustment screws are loosened to supply more lubricant, the various pipe connections should be examined. The first one to look at is the pressure pipe running to the tank. The first essential is to make sure that the tank filler cap seats securely, and that the leather washer is interposed as packing under the cap. Disconnect the pipe next to the check valve and with the motor running note if there is any pressure, i.e., if impulses from the

exhaust can be felt on the hand. If not, the nipple of the exhaust manifold or pipe should be removed and cleaned as it may be choked with carbon, especially if considerable oil is fed to the motor. The check valve near the tank may also be fouled up, due to foreign matter. This should be taken apart and cleaned, replaced, and the engine again started for testing the pressure. A simple method of quickly locating the fault in a system of this kind is to disconnect the pressure pipe at the tank and blow through the check valve member. If the tank and oil pipe connections are tight the oil will flow through the sight feed glasses, and it will be apparent that the trouble is due to not enough pressure being supplied the tank.

Leaks may exist between the sight feed glasses and their holders, and this is usually denoted by leakage of the lubricant around. the bottom of the glass. In disassembling and readjusting this member, care should be emphasized after new packing washers have been replaced, when readjusting not to screw down the fittings against the glasses too tightly as the glasses may be broken. When the glass fills up with lubricant, which is a sure indication of a clogged feed pipe, that member should be removed and thoroughly cleared by compressed air blast or steam under pressure. The steam is to be preferred as it will heat up any solidified wax or grease in the pipes. These sight feed glasses are apt to accumulate dust and dirt, especially as they are mounted in an exposed position in order to note at a glance if oil is dropping properly. A suggestion is given at Fig. 222, A, for removing dirt when the parts are difficult of access with a cloth, which is especially true when the sight feeds are assembled in a manifold fitting, as shown at B, where they are placed directly on the dash. A coarse, soft string is used, a couple of turns being made around the glass, then by imparting a sawing motion to the ends of the cord the encrusted deposit will be easily removed.

In those lubricating systems having individual leads running from a mechanical oiler, if failure of oil to reach the bearing is not due to a broken or constricted feed tube the trouble must exist at the pump supplying that member. The common fault in plunger pumps is failure of the check valves to seat properly,

this being due generally to dirt in the oil. Of course, if the main driving means fails the pumps will not move and no oil will be circulated. Oil pumps are not so apt to wear out as water pumps

Fig. 222.-Showing Simple Method of Cleaning Sight Feed Manifold Glasses at A and B. One Method of Curing Smoky Motor shown at C.

are on account of the lubricating properties of the oil, which tends to minimize depreciation by keeping friction at a low point.

Method of Curing Smoky Motor.-The owner of a practically new car was much annoyed with a smoky exhaust which clearly indicated that oil was working by the piston rings, and that this

condition was evident even when the level of oil was below the point recommended by the makers of the car if the motor was run at high speeds. It was evident that the trouble was not due to mechanical depreciation as the car was practically new. After considerable study a cheap and successful remedy for the trouble was devised.

The cylinder head was removed, the connecting rod bearings were loosened and the four pistons, after marking each, were removed. Next the wristpins and connecting rods were taken off, and each piston, after taking out the two lowest piston rings, was chucked up in the lathe separately. A small groove, a sixteenth of an inch in diameter, was cut into the piston, as shown in Fig. 222, C, at an angle of 45 degrees. The cut started from the edge of the bottom of the next to lowest piston ring groove. This cup was also one-sixteenth of an inch in depth, thus forming a cupshaped groove the entire circumference of the piston. Next the piston was drilled at the same angle of 45 degrees with a one-sixteenth inch drill. These holes, about one inch apart, were drilled clear through the piston. The effect of this groove was to collect the oil backed up by the bottom piston ring on the downward stroke. The small holes drained the oil into the inside of the piston and thus back to the crankcase.

The rings were replaced, the wristpins and connecting rods put back, the pistons slipped into the cylinders and the connecting rods tightened up. Next the cylinder head was replaced and oil put into the crankcase, the level of which was raised one-quarter inch above normal. When the motor was started the abnormal amount of smoke which the little engine had formerly produced failed to appear. After using his car a month, the owner called at the garage to state that the job had proved satisfactory. A repair of this kind can be made only when there is sufficient wall thickness to the piston.

Simple Oil Filter.-There are many occasions when oil is drawn from a motor crankcase or sump when it still possesses lubricating qualities, but is unsuitable for use owing to the presence of dirt. Even if an oil is unsuitable for cylinder lubrication, it may still possess sufficient lubricating value to be used around the unim