How to Read a Cam Grind
Reading a cam grind specification chart requires basic knowledge of the camshaft's function. The cam grind number itself is a camshaft specification code to designate the manufacturer's different cam designs, each optimized for a different engine application. The other specs included in the cam grind specification chart are lift, duration, overlap and lobe separation angle.
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Instructions
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Notice the height of the cam lobes. When the engine is in operation, the camshafts constantly rotate. As the cams rotate, the lobes press against the valve rockers. This in turn compresses the valve springs, which opens the cylinder head valves, allowing air and fuel to enter the engine cylinders. The height of the cam lobe determines how far the valve opens. This measurement is known as the cam lift.
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Notice the elliptical shape of the cam lobes. This shape allows each lobe to smoothly open and close the cylinder head valves. The wider the angle of the lobe ellipsis, the longer the valve will be held open. This measurement is known as the cam duration. When manufacturers design aftermarket camshafts, they custom grind the angle and height of each cam lobe. This is why different camshaft specifications are known as "grinds."
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Consider the function of dual-cam engines. In these engines, there is a designated camshaft that operates the intake valves, and a second camshaft operates the exhaust valves. The cam lobes must be designed such that the intake and exhaust valves open in the most optimum pattern to increase airflow into and out of the engine. The measurement of separation between the peak points of the intake and exhaust cams is known as the lobe separation angle.
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Examine a cam grind specification sheet. The lift value of the cam lobe is given in inches. For example, a cam grind with a .454-inch lift will open the valve retainer .454 inches at its peak angle. The cam duration is given in degrees. This is the measurement of how long the valve remains open relative to the camshaft's rotation. The greater the degree value, the longer the valve is held open.
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Tips & Warnings
Always research the requirements of your engine before purchasing upgraded camshafts. If the cam lift or duration values are too high for your engine setup, serious damage to the valves and pistons can occur.
