They were merely concerned with getting the engines to run at slow speeds. The engineers of the late 1800's were only concerned with harnessing power of the gasoline and air explosions in an internal combustion engine to propel an automobile, hopefully, a little faster than a horse. In the old days, the first four cycle engine had very short valve timing, but rightfully so because these were slow speed engines. Its purpose is to operate the intake and exhaust valves in the correct timing with the piston as it sequences thru the four strokes. The camshaft is connected via the timing chain and sprockets at a 1:2 ratio to the crankshaft and therefore revolves once for every two turns of the crank. Two revolutions complete one sequence of the four strokes. 4 cycles x 180° = 720° or two revolutions of the crankshaft. Each stroke represents one-half of a revolution of the crankshaft or 180 crank degrees. You probably already know the four basic strokes of the four cycle engine: INTAKE, COMPRESSION, POWER, and EXHAUST. Indeed, cam degreeing is simple, but first let's make sure you have a good understanding of the cam's function in the four cycle engine.
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