A type in which all valves are located in pockets at opposite sides of the cylinders.
A type in which all valves are located side by side in one pocket, on either right or left side of the cylinder.
A type in which all valves are located in the cylinder head, placed vertically or at an angle.
There are also several other types which are combinations of those depicted above, having one valve in the head and the other in a pocket at the side, or both valves in a pocket at the side, one being located above the other.
The first and second types, namely the T-head and the L-head, are by far the most popular type used in commercial cars. However, quite a few of the others may also be found. The first three types possess an advantage in that all working parts may be inclosed and thoroughly protected from grit. They also present a neater appearance in that it is a simple matter to keep them clean, as all parts are lubricated internally.
The writer is presenting several illustrations which depict these various types taken from illustrations furnished by the various makers of these engines.
Fig. 13 depicts the conventional type of T-hend cylinder in which all the intake valves are located on the right side and all the exhaust valves on the left side, the valves being inserted through openings in the combustion chamber, which are covered by valve port plugs that carry the spark plugs.
Fig. 14 depicts the conventional type of L-head cylinder in which all intake and exhaust valves are located on the left side, the intake and exhaust valve of each cylinder being located side by side in a pocket. The valves have conical seats, as those depicted in Fig. 13, and are also inserted through openings in the combustion chamber, which arc closed by the valve port plugs. The plugs which cover the intake valve openings carry the spark plugs, while the exhaust port plugs carry the relief or priming cups. In this motor the valve springs are of conical shape, the object of this being to obtain a more gradual seating of the valve. The valve stems and operating parts are also enclosed: however, two aluminum plates are used, each covering four valve stems.
They are retained by a wing nut and stud, which may be quickly removed.
Fig. 15 depicts a valve in the head-type cylinder in which the valves are placed vertical. The valve stems only pass through the cylinder and for this reason the cylinder is divided in two parts at the top of the compression space. Valve guides are used to provide a bearing for the valve steins, and coil wire springs keep the valves closed. This construction presents an advantage in that the entire compression space may be machined to a polished surface, thus reducing the tendency for carbon to collect in the combustion chamber and dividing the cylinder at this point also facilitates the removal of carbon when it does form. If this type of cylinder were cast in one piece it would l>e necessary to remove it from the engine in order to grind the valves, unless they were mounted in cages which could be removed.
Fig. 11 depicts one type of the combination of types and is the only arrangement resorted to by American makers, the other type of placing one valve over the other has never been used on commercial car motors to the writer's knowledge, the combination in this type being identical with the construction of the other types from which they were derived, one valve being located in a pocket and operated directly, while the other is located in the head and is carried in a cage in the cylinder head and operated through a rocker arm.
During the past year there has been a tendency to divide L-head cylinders of the motor used in light delivery wagons, so that part of the crank case could be cast integral with the cylinders. This construction, of course, presents advantages in the removal of carbon, valve grinding, finishing of the combustion space, as well as reducing the cost of manufacture. It remains, however, to be seen just what popularity this construction will gain in the heavier types of motors.
There are various ways of grouping cylinders, as they may either be cast single, in pairs or en bloc. Where they are cast single the motor becomes of considerable length and, of course, requires a much longer hood; this additional space when added to the loading compartment would naturally be of considerable advantage. Casting them in pairs shortens the motor somewhat. However, the ideal construction is obtained when the cylinders are cast en bloc, which permits of the shortest possible hood length. It also presents an advantage in the shorter length of the vital parts such as the crank and cam shaft, crank case, etc., as the space wasted can be put to good advantage by the increasing of the main bearings and the shortening of the unsupported parts of these shafts.
This method of cylinder grouping can be applied to any type of motor, or valve arrangement, and is not dependent upon any one construction. En bloc cylinder construction does present a very simple and neat motor, especially when all parts are properly enclosed.
Fig. 13. Sectional View of T-Head Cylinder.
Fig. 14. Sectional View of L-Head Cylinder.
Fig. 15. Sectional view of Valve-in-Head Cylinder.