Camshafts for strong, low-end torque are desirable in applications where normal driving occurs. Examples are typical stop-and-go traffic or in situations where heavy loads are being pulled or towed. An engine that produces more torque can also be more economical.
Torque is the measurement of rotational force generated by an engine. This force -- which all engines produce -- is a function of the engine's leverage. A larger displacement engine with a long-stroke crankshaft is capable of producing more torque.
The engine speed at which torque and horsepower are made are dependent on the ability to flow air. Components such as cylinder heads, intake/exhaust system and the camshaft all play an important role. Properly matched, the engine can be programmed to produce its maximum outputs at predetermined revolutions per minute (RPM) ranges.
Factory camshafts are designed to meet a broad range of performance needs and don't always target a specific goal. Aftermarket camshaft vendors can incorporate more precise specifications with (sometimes) more-advanced technology.
The primary feature of a cam designed for low-RPM usage is short, valve-opening duration. Duration is the amount of time (in crankshaft degrees) which the valve is open. Increasing the duration has the effect of moving the RPM range higher, which is not the goal of a high-torque engine. Increased lift can allow more air and fuel into the cylinder which creates the possibility for more power, and narrower or wider lobe center lines affect how broad the power band will be.
