Cam valves are actuated by levers which receive their motion from a camshaft that lies along the cylinder head. This camshaft is driven by the engine shaft through the intermediation of the vertical governor shaft and two sets of helical gears.
To allow the valves and cages to be lifted without the re moval of the entire rocker arm and shaft, the rockers are in two parts. These two parts are held together by one bolt A while two dowel pins B preclude the possibility of the parts being improperly aligned on reassembly. One end of the rocker carries a hardened steel roller while the other end is fitted with the adjusting screw G, which screws into a steel pin and is locked by the nut H.
Valve Lever adjusting screw enables the operator to_obtain the required clearance between the roller and the cam when the valve is closed. The rocker arm is held against the valve stem, and the clearance is measured between roll& and cam by ordinary thickness gages. The clearance values that are correct for all sizes of the Busch-Sulzer Type B engines are as follows: Admission valve cam clearance. 0.012 inch Exhaust valve cam clearance 0.018 inch Fuel valve cam clearance 0.004 inch Starting valve cam clearance 0.012 inch Since the clearances are established when the engine is cold, it becomes necessary to note whether the valves close after the engine has become warmed. If not, the adjusting or push screws can be backed off to give these values. Figure 81 is the usual valve, timing on this engine.
Camshaft Layout.—Figure 82 is a schematic outline of the actuating valve levers of the Busch-Sulzer engine. The lever shaft g is supported by the pedestal bearings, better shown in Fig. 83. The lever d controls the exhaust valve, while a actuates the air admission valve, and the lever b governs the fuel valve, the lever c opening the air starting valve in starting the engine. The levers b and c are mounted on an eccentric bushing which is supported by the shaft g. In starting, the lever o moves the eccentric bushing to the "starting" position where the fuel lever b does not engage its cam b; this movement brings the starting lever c'into contact with its cam c. This action is carried out on the two starting cylinders; on the two idle cylin ders the eccentric handle is moved to the neutral position, cutting out the fuel valve. It should be understood that only
the two starting cylinders have the starting valves. Figure 83 also shows the cam arrangement.
McIntosh & Seymour Diesel Valves.—The admission and exhaust valves of this engine follow the form shown in Fig. 84. Both valves have the same dimensions, the difference between the two being the removable seat, used on the exhaust valve; the valve seats have a 60-degree angle with the stem. This seat is an alloy-steel ring held in place by two countersunk screws. In renewing this ring it is very essential that the surfaces be thor oughly cleaned. Occasionally the ring is slightly distorted when received; it must be ground true before it is placed on the valve. The exhaust and admission valve cages are of the same external dimensions. They differ only in the exhaust cage having a water cavity around the valve stein. The cages rest in machined cavities in the head, the joint at the point a being sealed with a copper gasket. The gasket must be of the proper width to eliminate danger of cramping when the cap is placed over it. Figure 85 shows the exhaust valve and its cage.
To disassemble the valve, the pin b, Fig. 86, is driven out of the valve stem, and the bushing a is removed. The spring cap d is pushed downward, allowing the slotted ring c to be slipped from around the valve stem. This being done, the spring cap and the spring are withdrawn from the top of the cage while the valve can be removed through the bottom end of the cage.
Camshaft.—The camshaft lies along the cylinder heads, rest ing in bearing pedestals mounted on extensions from the cylinder castings.. The camshaft is driven, through helical gears and a vertical governor shaft, by the main engine shaft.
Figure 87 shows the valve rocker arrangement where d is the exhaust rocker, a is the admission rocker, b the fuel rocker, and c the air starting rocker. The cams for b and c are in one piece; the engine is started by shifting the starting roller c until it con tacts with the starting cam; a small lever is provided on the rocker for this purpose. After the engine fires, the roller c is moved out of contact with its cam.