How to Choose the Right Camshaftby Moss Strohem
The camshaft is one of the single most important engine components that impacts an engine's power output and performance. All four stroke-cycle engines are equipped with cams, and the purpose of them is to precisely "time" (control) the opening and closing events of the intake and exhaust valves. Its design must match the type of driving and other components of the engine/car, so selecting the right camshaft for the application is essential.
Determine, Research, Select
Determine the principal use for the vehicle. While a vehicle can meet many needs, there is generally little need for all-out, wide-open-throttle performance at all times. Most cars and trucks are used in situations where there is frequent stop-and-go driving or driving at freeway speeds. While an efficient cam design can improve power and economy in these engine speeds ranges, one that is too big can have detrimental effects. Likewise, a cam that is too "small" can also hinder performance. Be completely honest about the application when choosing the right camshaft.
Identify, learn and understand camshaft timing events and how they impact valve action and engine performance. If needed, find a trusted individual who understands this information. The most significant determinant of cam performance is "duration."
Duration is the amount of time--in crankshaft degrees--a cam has the valve opened. Duration is measured two ways: with advertised duration, and in duration at .050-inch tappet lift. The latter is a universal standard by which to compare camshafts. The greater the duration (length of time a valve is open), the higher in the RPM range the power production of an engine takes place. Too much and the engine will make disappointing low RPM power.
Other important terms are valve lift (the total distance a valve opens); lobe separation or lobe centerline angle, also known as LCA (the distance in degrees which separates intake and exhaust cam lobes); and overlap (the amount of time in degrees which both the intake and exhaust valve are simultaneously open).
Decide which type of cam follower (tappet) is to be used. Current camshafts are available in two forms, each having two types of lifters.The lifter types are either flat-tappet or roller tappets. Each is available with either a hydraulic or mechanical (solid) lash design.
Hydraulic lifters are operated with zero valve lash--that is, there is no clearance between the valve tip and the valvetrain. A hydraulic plunger within the lifter automatically compensates for this tolerance. Solid lifters require periodic checking and maintenance and do not operate as quietly as hydraulic lifters..
Contact a manufacturer or retailer for final evaluation and recommendations. Most camshaft companies have trained technicians available to answer questions and offer suggestions based on input from the car owner. Again, the key point is to be candid about the car's application--how it will be driven most of the time.
- check When face with a choice of cams that seem to provide similar performance objectives, select the "smaller" camshaft.
- close Beware of a camshaft with too much valve lift, too much duration, and/or too little love separation (LCA). Any of these three items could cause interference between the valves and pistons. On some engines, interference between valve guides and valve spring retainers can also be an issue with too much lift.