1942 - 1947 Chevrolet Shop Manual



6-22

tion. Bend pipe on right side of block to clear the push rod cover. Then bend the upper portion of pipe to pass through the hole in the cylinder head. Connect the pipe to the valve rocker shaft coupling. Fill the cooling system with water, start the engine and check all connections for both oil and water leaks. CYLINDER HEAD ASSEMBLY One of the most important units of any valve-in-head engine is the cylinder head. It contains not only the combustion chambers and spark plugs but the valves, inlets ports, exhaust ports and the necessary water passages to maintain the proper temperature of these important parts. The Chevrolet cylinder head is designed to give a compression ratio of 6.50 to 1 and 90 horsepower (the same head giving 6.62 to 1 ratio and 93 horsepower on the heavy duty 235.5 cubic inch engine.) The combustion chamber is designed for use with a flat top piston that provides exceptionally compact combustion volume on the exhaust valve side where the spark plug is located. On the intake valve side the head is machined so that, except for a shallow recess in which the intake valve is located, the bottom face of the head over the piston is flat and is separated from the piston at top dead center by the thickness of the cylinder head gasket only. The valves are so located that they permit the incoming charge of fuel mixture to enter the combustion chamber, do its work, and leave the chamber after its work is done, without restriction, making use of the volume of mixture efficiently with the least possible disturbance. This type cylinder		VALVES Chevrolet valves have a high resistance to heat, corrosion and pitting. They are made from sili-chrome stainless steel by what is known as an extruding process. This manufacturing process is a development of Chevrolet and it shapes the rough valve in one operation. From the rough forging to the finished product all operations are carefully performed and inspections are frequent. The end of the valve stems are hardened electrically to reduce wear at the contact point with the rocker arm. Valve Guides The clearance between the valve guides and the valve stems is very important. Lack of power and noisy valves, in many instances, can be traced to worn valve guides. The intake valve guides should be checked with a new intake valve and the exhaust guides with a new exhaust valve, because the diameters of the stems are different on these parts. The exhaust valve guide is designed to bring the inner end of the guide flush with the inside of the valve port. With this design the heat dissipating properties are increased and aids in eliminating sticking valves.

head is the result of many years' experience in providing ample water space around the valves and spark plugs in addition to a means for most effective distribution of water. The coldest water is taken

into the cylinder head and directed toward the	Fig. 46—Cylinder Head Water Nozzles
valve seats by means of • eight small copper nozzles pressed into the lower part of the head. There are three kinds of these nozzles used—long and short type, each with a single opening used to direct single streams of water to the single exhaust valves at the end cylinders and another with two openings which direct two streams of water to the other exhaust valves, Fig. 46.
		Fig. 47—Removing Valve Guide