Engine Rocker Arms
A rocker arm is an oscillating lever that conveys radial movement, from the cam lobe, into linear movement,in order to open the poppet valve. One end of the rocker arm is lowered and raided by the rotating lobes on the camshaft while the other end acts on the valve stem. As the camshaft lobe raises the outside of the rocker arm, the inside of the arm will press down on the valve stem which opens the valve. As the outside of the rocker arm starts to lower, the inside of the arm will lift which will allow the valve spring to close. The rocker arm is located inside the valve cover one the engine.
The leverage of the rocker arm is determined by the rocker arm ratio. This ratio is the distance from the rocker arm's center of rotation to the tip, divided by the distance from the center of rotation to the point acted on by the camshaft or pushrod. The ratio of the rocker arm refers to the amount of movement on the valve side of the rocker arm in comparison to the pushrod side. A higher ratio rocker arm is capable of moving more air and fuel which can increase engine power if everything is set up right.
Rocker arms are made out of a strong material such as steel or aluminum to stand up to all the force and pressure exerted on them. Keeping the weight of the rocker arm at a minimum is essential because it is part of the engines reciprocating weight which determines the operating speeds of the vehicle. In a normal vehicle, the balance between providing a reasonable amount of strength, weight, and economical cost is the main factor. In a high performance vehicle, cost and longevity may be sacrificed a bit for the performance aspect of a part.
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