Performance Camshafts Aberdeen SD
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Choosing Performance Camshafts
By Scooter Brothers
Americans are very enthusiastic about their automobiles. Therefore, when they purchase, rebuild or even imagine their dream cars, a tremendous effort is put forth to make sure it is exactly what they want. Because the engine is arguably the most significant element in the performance of the car, it is very important that the internal components be properly selected so that the engine, and the entire vehicle, can achieve the desired results.
The camshaft is the main component that will help enhance the performance characteristics of the engine, but it is important to understand what role the cam plays in the engine and how the cam specs can be changed to optimize the performance. The cam causes the valves to open and close, and that regulates how much air and fuel enters and exits the combustion chamber. As is the case with most decisions, there are clear tradeoffs that must be made with cam selection. It is critical to select the proper cam for the size engine, the components in the engine, and ultimately what the expectations of the vehicle will be. Chances are that if we are even considering a high performance camshaft, the car will be used for some type of recreation, and it must be fun to drive. It’s best to take a good look at things before making any decisions.
There are two basic types of camshafts used most commonly in most V8, pushrod style, mild performance street engines. The older and most traditional designs used a flat faced hydraulic lifter, while most newer designs utilize a hydraulic roller follower. While it is commonly thought that the decrease in friction is the main advantage of the roller cam, the benefit is actually mostly that the roller design allows the valve to be opened and closed at a much faster rate, resulting in more area with shorter seat timing.
Seat duration, which is the distance between the opening and closing point of the valve, measured in crankshaft degrees, is measured several different ways. The current SAE specification for rating seat duration of camshafts is .006˝ valve lift, which corresponds to about .0035˝ to .004˝ tappet lift. However, while the OEMs have adopted the SAE criteria in late model applications, earlier camshafts were typically rated at far lower tappet lifts. Some factory performance grinds of the 1960s and ’70s were rated as low as .0001˝ to .001˝ tappet lift. High performance aftermarket cam manufacturers normally rate their hydraulic cams seat duration at either .006˝ or .004˝ tappet lift.
It is very important to understand how the cams are rated prior to comparing a stock cam to an aftermarket cam, and before selecting a cam. The very beginning and end of the lift curve on a stock cam is usually such that the valve opens slowly and sits down very gently on the seat. This is particularly important for noise and seat recession, as well as overall durability. It is the area i...