If you look at the similarities between a human and an engine, I would compare them like this - The oiling system is the heart; it transfers vital fluids (oil) to the critical areas of the engine. Without it the engine would not live very long. The intake system is the lungs, it takes oxygen and mixes it with fuel to ultimately have its energy converted to power once inside the engine. This then makes the piston, rod, and cranks the muscles of the engine. They take the energy from the lungs and convert it into mechanical work; ultimately what turns your tires. Much like a person, all of these operations are needed to survive, but a sound brain is still the most important of them all. The valve train is the brain of the engine. It tells the engine when to breathe in and when to breathe out. It also classifies the engine as to what characteristics it will have. Will it make a lot of torque or will it make high rpm horsepower? You could call this its temperament or attitude.
Without the valve train the engine wouldn’t know how to think. If the engine isn’t told exactly when to breath, or open and close the intake and exhaust valve, it will not function properly- if at all. The camshaft is the deciding factor as to what and when the valve opens. The breakdown of the valve timing is an article within itself. I would like to go over at this time what parts are related to the “brain” of the engine and some considerations that go into their design.
Before we go too far, I would like to talk about inertia so you can understand how it relates to your valve train components. Inertia is defined as, a property of matter in which it remains at rest or in uniform motion in the same straight line until acted upon by some external forces. In other words, things in motion like to stay in motion. You see this every time you try to turn your race kart; it tries to keep going straight and takes a high counter acting force to make it change direction. Everyone also knows that they wouldn’t want their tires filled with lead because the higher the mass of an object the higher the inertia, and the more it resists a change in direction, making it slow to accelerate, and just as hard to stop. You are probably wondering why this relates to the valve train. Hopefully, by keeping these thoughts in the back of your mind, objects in motion want to stay in motion, and the higher the mass (weight) the more an object will resist a change in direction, you can see how it could affect the valve train's function.