All About Engines

2i8 All About Engines past the piston rings, and the interior has to be cleaned out by an oxy-acetylene blow-pipe flame. The valves work in a small combustion chamber on the far side of the drawing, and not, therefore, shown in the figures. They and the method of operating them are shown separately in Fig. 124. The adjustment for wear is made by turning a nut, which lengthens the spindle, and differs, therefore, from that shown on page 210. The valve plunger also has a small piece of compressed fibre inserted to reduce the noise. The valves are ground into their seats with jeweller’s rouge in order to obtain a perfect fit, and occasionally they need to be reground. The sparking plugs are fixed just above the valves, and the order of firing in the four-cylinder engine is 1, 3, 4, 2, this being the order in which the cylinders compress their charges. The water is caused to circulate by a small centri- fugal pump on the same spindle as the magneto, and marked 19 on Plate 19. After passing round the cylinder jackets it flows by means of the pipe marked 9 into the top of the radiator, which is fixed just in front of the fan at the very front of the car. This fan draws air through the nest of tubes and aids the cooling. Nevertheless the water in the radiator becomes very hot in warm weather. The cylinders of this engine are 3^ inches or 90 millimetres bore, and 4} inches or 121 millimetres stroke. The speed is 1,200 revolutions a minute, and the speed of the car can be varied from 7 to 28 miles per hour. For higher powers six cylinders