This is accomplished by lining up the 1⁄4, or 1⁄6 D-C mark on the flywheel rim with the center mark on the cylinder block, and means that 1⁄4, or 1⁄6, pistons are on upper dead center of the compression stroke, the flywheel is then turned a trifle until the marks E-C, or Ex-C, is at upper dead center and in line with the mark on the cylinder block. This means that the exhaust valve closes at this point. The cam shaft is then turned in the running direction and the cam shaft gear meshed at the valve closing or seating point. This is all that is necessary as the other cams take up correct operation when any one cam is set properly.

Another method of valve timing used by some motor manufacturers is shown in [Fig. 14]. It is simply necessary in this case to line up the prick punch marks on the timing gears—after getting the first position on upper D-C of the compression stroke—to acquire correct valve time. No definite or average scale can be given for valve timing, as all different types of motors are timed differently. These instructions must be secured from the manufacturer when the motor is not marked.

Cylinder Marks Camshaft
Gear
1-4 Pistons
on Upper
Dead Center
FLY-WHEEL MARKS
Running Direction of
Fly Wheel
MARKS LINED UP
Timing Gear
Punch Marks		Crankshaft
Gear

Fig. 14. Valve Timing Marks

Valve Grinding.—A valve-grinding compound can be purchased at any garage or service station or one may be compounded by mixing emery dust with a heavy lubricating oil until a thin paste is formed. The valve spring is released next by forcing up the tension with a screw driver or valve lifter. A small H-shaped washer is drawn from a groove near the end of the stem, which frees the valve; it can then be pushed up and raised through the guide. A small spring is placed over the valve stem. This spring should be strong enough to raise the valve one-half inch above the seat. A thin film of the grinding compound is evenly applied to the seating face of the valve head, a screw driver or ratchet fork is set in the groove on the head of the valve, and the handle rolled between the palms of the hands, covering about one-third of the distance around the valve seat; the valve is let up after the motion has been repeated four or five times, and repeated at another angle until the entire surface of the valve is smoothly ground and allows the valve to seat perfectly.

Valves.—The sleeve valve type of motor was invented several years ago by Charles A. Knight. He met with some difficulty in having it manufactured in this country because the lubrication system was thought to be inadequate and the poppet valve was then at the height of its popularity with the manufacturer of engines.

Knight took his engine to Europe and made some slight improvements on it. It was then taken over and manufactured by one of the large automobile manufacturing companies of that continent and is now being used by many of the celebrated automobile manufacturers of every country.

The principle of operation does not differ in any respect from the ordinary type of four cycle motor, except, that instead of having the poppet type of valves it has a set of sleeves which slide up and down on the piston. The sleeves are operated from an eccentric shaft by a short connecting rod and carry ports which are timed to line up with the ports of the intake and exhaust manifold ports at the proper time in the cycle of operation.

[Fig. 15] shows the method of timing the sleeves on the four cylinder engine. First, turn the motor over in the running direction until the marks (I-4-T-C) on the flywheel are in alignment with the marks on the cylinder casting. Turn the eccentric shaft in the running direction until the marks A, B, C, shown in [Fig. 15] are lined up, and then apply the chain.