conditions under which the power plant is operated. If the lubricating oil is introduced in excessive quantities a considerable portion will be forced into the combustion chamber, where it will be burned by the excessive heat present at that point and produce carbon deposit in the interior of the cylinder head. When an engine is supplied with too much oil the surplus will escape at all pos

Fig. 122.-Sectional View of Commercial Car Crank Case Showing Oil Supply by Plunger Pump.

sible bearing points and the wasted lubricant performs no useful serviee. If the oil is not supplied in sufficiently large quantities the bearings will heat because of the friction between their parts and some of the engine power will be lost. If the oil supply is interrupted through accidents, the part may heat up sufficiently so

Fig. 123.-Showing Oiling System for Engine Lubrication Employed on Packard Motor Truck

that the bearings will be burnt, cylinder and piston walls scored and other damage done.

Q. How can oil supply be regulated?

A. One of the advantages of the constant level splash system of lubrication is that the amount of oil required is determined by experiment at the factory and the motorist does not have to regulate the oil feed to any extent. The operator's responsibility ceases when the oil container has been filled with a sufficient quantity of good engine oil. On some of the individual pump mechanical oilers the stroke of the pumps may be varied to alter the oil feed. Sight feed lubricators are often provided with needle valves to regulate the amount of oil passing through the orifice they control in a given unit of time.

Q. Describe some typical lubrication systems used on high grade cars.

A. The oiling system of the Packard six cylinder motor i clearly outlined at Fig. 124. In this the oil is carried in a sump formed integral with the crankcase and is taken from that point by a pump and delivered to a manifold pipe extending along the side of the motor crankcase. This manifold communicates with the main bearings, as well as to the timing gear assembly at the front end of the motor. The crankshaft is provided with drilled passages so the oil supplied by the oil manifold lubricates the connecting rod big ends after it passes from the main bearings. The cylinder interiors, pistons, valve plunger guides, and other parts are thoroughly oiled by the oil spray always present in the crank A manometer or pressure gauge is carried on the dash board and is attached to the end of the motor oil manifold. This indicates at all times if oil is being delivered to the bearing points. If the pressure of oil becomes too great in the manifold as sometimes occurs at high engine speeds, a relief valve is provided which permits the excess lubricant supplied by the pump to bypass back into the crankcase interior.

case.

The system of lubrication employed on Packard trucks is shown at Fig. 123. In this the oil is drawn from a tank by an oil pump and forced through the sight feed on the dash, back to the crank

case interior, where it collects in the front and rear crankcase compartments to a level indicated by the petcock screwed into the sides of the crankcase. The interior of the engine is thoroughly lubricated by the splash system.

In the Pierce Arrow cars practically the same arrangement as used in the Packard six cylinder and several other leading cars is used. This system is depicted at Fig. 125 and involves the use of a gear driven oil circulating pump having its suction side connected to the sump at the bottom of the crankcase and its delivery pipe to a manifold which goes to the main bearings of the drilled out

Fig. 125.-Oiling Method Used in Lubricating Pierce Arrow Six-Cylinder Power Plant.

crankshaft. A feature of this system is the use of an oil strainer or filter screen on both suction and delivery sides of the pump. Both of these screens may be readily removed for cleaning purposes and insure the delivery of only perfectly clean oil to the bearing points. Two petcocks are provided on the side of the crankcase. The one at the bottom is a drain cock through which the sump may be emptied at any time while the testcock indicates if the oil level in the sump is sufficiently high.