VALVE CONSTRUCTION, TYPES, AND OPERATION 8-CYLINDERED V-TYPE ENGINE

Valve Head	Removable Plates	Cam Shaft	Valve Head
Valve Seat			Valve Seat
Tappet for Adjusting Valves			Tappet for Adjusting Valves

Fig. 11. 8-Cylinder Valve Arrangement

[Fig. 11] shows the location of the cam shaft, valves, and tappet adjustment, on a V-shaped engine. The cylinders of this type of engine are arranged in two blocks, consisting of four cylinders in each, set directly opposite each other on an angle of 90°. The connecting rods from opposite cylinders are yoked and take their bearing on the same crank pin. This arrangement allows the intake and exhaust valves of each opposite cylinder to operate from a single cam shaft, or in other words the entire sixteen valves are operated by a single cam shaft carrying eight cams. Consequently an eight or twelve cylindered engine is identical in regard to valve timing to either a four or six cylindered engine.

Valve Head

Valve Seat

Valve Guide

Valve Stem

Valve Spring

Sp. Seat

Cap Screw

Tappet

Lock Nut

Guide Bushing

Push Block

Roller

Cam

Fig. 12. Poppet Valve

[Fig. 12] shows a poppet valve. This type of valve has only one adjustment, called the tappet. The adjustment is made by turning the cap-screw out of the push block until the head comes into contact with the valve stem. The lock nut on the cap screw is then turned down tightly to the push block to hold the adjustment. A strong spring is placed on the valve stem which causes it to close quickly and remain closed until it comes into contact with the cam.

Valves are set and operate in three different positions as shown in [Fig. 13]. The exhaust valve in this case seats on the floor of the combustion chamber and is operated by the stem which extends through the casting to the tappet, while the intake valve seats on the upper wall of the combustion chamber and is operated from over head by a push-rod extending from the tappet to a rocker-arm. When both valves are operated from above and seat on the upper wall of the combustion chamber the motor is referred to as the overhead valve type of motor. In the majority of motors both valves seat on the floor of the valve chamber.

	Rocker Arm
	Valve Stem
Valve Open	Valve Seat
Combustion Chamber	Tappets
Cam
Cam Shaft
Overhead Type Valve	Push Rod
Poppet-Type Valve

Fig. 13. Valve Types, Location and Operation

Valve Timing.—Valve timing is usually accomplished by setting the first, or exhaust valve cam, to correspond with a mark on the flywheel and cylinder (shown in [Fig. 14]).

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.

Timer
Shaft
Sprocket

Crank Shaft Sprocket

Fig. 15. Knight Valve-Timing Marks—4-Cylinder

To check up on the timing, back the flywheel up an inch or two and insert a thin piece of tissue paper into the exhaust port and turn the engine in the running direction until the paper is pinched, which signifies that the valve is closed. The marks on the flywheel, timing gears, and the crank case should be in alignment. [Fig. 16] shows a diagram of the timing marks on the eight cylinder Knight engine. The method of timing this engine is as follows: (1) Turn the engine over until the marks I-4-R-H—D-C align with the marks on the crank case. (2) Turn the eccentric shaft and sprocket until the arrows shown in [Fig. 16] are in line with the guide marks on the front end of the chain housing. Then put on the chain and check up the timing, using the thin piece of tissue paper.

Eccentric Shaft
Sprocket Hub

Mark on
Eccentric Shaft
Sprocket

Guide Mark on
Crank Case

Crank Shaft
Sprocket

Fig. 16. Knight Valve-Timing Marks—8-Cylinder