Saturday, November 23, 2013
Effects of Cam Timing on a V8
Camshafts are long metal rods with various ovals of shaped metal (called lobes) that control the opening and closing of engine valves. The valves are precisely timed to open and close based upon combustion within the engine cylinder. Manufacturers tend to create mild camshafts that produce smooth even idle, and help an engine produce a broad range of power. You can alter the camshaft timing by replacing the factory camshafts with aftermarket units, which is a popular upgrade option particularly among V8 owners.
Camshaft Location
The camshaft will be located in different places based upon the design of the V8. In a pushrod V8 one camshaft is buried in the center of the engine block. Metal rods (called pushrods) used in conjunction with rocker arms connect the camshaft to valves. In a overhead camshaft V8 (OHC), either a single (SOHC) or dual (DOHC) camshafts sitting above the engine banks. Lifters and springs are used to actuate the valves. A SOHC may have rocker arms since only one camshaft operates both banks of cylinders.
Camshaft Operation
The camshaft rotates based upon a chain that runs from the crankshaft. As the camshaft spins, the lobes on the camshaft cause the valves to open and close. Manufacturers create camshafts with mild timing that insures the intake and exhaust valves are not open at the same time -- called overlap. While earlier V8s employed fixed timing, todays modern engine management systems allow for variable timing, where the valve timing is changed by moving the camshaft to adjust for engine speed, which in effect advances or retards the valve timing.
Performance Improvement
Large performance gains can be obtained with a aftermarket or altered factory camshaft that advances timing. When an engines intake and exhaust subsystems are altered, this changes the airflow of the engine, and thus a revised camshaft can optimize valve operation. In addition, by allowing for some overlap (where both the intake and exhaust valves are open at the same time), the engines performance is increased at the expense of poor and choppy idle (which is a plus to most V8 enthusiasts).
Tuning
To optimize camshaft performance, you must have the vehicle tuned after installation. While the camshaft controls timing of valves, the fuel and spark (injectors and coils) will need to be adjusted to match the revised airflow.
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