Chevrolet's 1935 six-cylinder valve-in-head engine is more powerful,
quiet and economical.
While this engine is not new, it has several features and many refinements which are the result of careful research and development by Chevrolet engineers with the cooperation of General Motors Research and the General Motors Proving Grounds, over a period of years.
These engines are designed and manufactured with the thought of building a balanced power plant that will give satisfactory service. This new six-cylinder engine is a further refinement of the sturdy six-cylinder engine that has given more than 4,000,000 Chevrolet owners perfect satisfaction for many millions of miles.
This engine incorporates many features such as a rigid crankcase,
69-pound crankshaft, balanced cast iron pistons, electroplated,
cylinder head with water nozzles to control the temperature around
the valve seats, overhead valves and many other refinements too
numerous to mention here, but which are fully covered further on
in this chapter.
All Chevrolet Engines are "Four Cycle," which means there are four complete strokes of the piston or two complete revolutions of the flywheel to complete one cycle.
1. As the piston starts downward in the first stroke of the cycle the intake valve is opened. The motion of the piston creates a vacuum in the ASSEMBLY cylinder and draws a charge of gas from the carburetor through the valve opening.
2. When the piston reaches the bottom of its stroke and starts upward on the second stroke of the cycle, the intake valve closes and the piston compresses the gas that is drawn in to the combustion chamber in the cylinder head.
3. As this piston reaches the end of its upward stroke the compressed gas is ignited by an electric spark which occurs at the points of the spark plug and the resulting explosion or expansion pushes the piston downward, turning the crank-shaft on the third working stroke of the cycle.
4. On the upward stroke of the piston, the exhaust valve is opened and the piston forces the remaining burned gas out through the exhaust port, leaving the cylinder empty and ready for the beginning of a new cycle.
Like any piece of machinery, the engine of any motor car or truck needs periodical attention and care. Upon this periodical care depends, to a great extent, the performance and economy of the engine.
The engine should be tuned at specific intervals as well as the valves ground to expect the maximum amount of economy. This procedure is fully covered later on in this chapter.
The life of the engine, to a great extent, is dependent upon the rapidity at which moving parts become worn. The minimum amount of wear can be obtained only through the use of correct oils properly applied.
The cylinder block used in Chevrolet engines is a grey iron casting produced in the largest grey iron foundry in the world.
It is heavily ribbed at the points of maximum stress to prevent deflection under loads. It is machined on modern machines, all operations being located from two master holes which assures perfect alignment of all operations.
The cylinder walls are bored and honed to a mirror-like finish and held to within 1 thousandth of an inch out of round and taper.
Genuine Chevrolet pistons are cast iron electroplated, with a solid skirt with three ring grooves located above the piston pin holes. They are of unusual design, being cam ground out of round. This out of round piston compensates for heat expansion along the line of the piston pin bosses.
The lower piston ring in the piston is an oil control ring with ports to allow excess oil, scraped from the sides of the cylinder walls, to be returned to the inside of the pistons and then to the crank-case, by means of holes drilled in the ring grooves of the piston.