Increasing the displacement of production engines by using a crankshaft with a longer stroke is a popular way to gain more power. These "stroker engines" are used in many different applications -- towing, street driving, boating and offroad racing and competition. The modification also changes the characteristics of the engine by adding increased low-RPM torque and power (all other things being equal), though the effective power range is reduced by a few hundred RPM. A cam specifically designed for the new, increased stroke will restore and/or optimize the engine performance.
Evaluate the purpose of the car (truck, boat, etc.) the stroker engine is being used in. A vehicle that is used for daily operation or for low-speed operation will use a camshaft with much milder valve timing events than one which will be used in higher-performance applications.
Weigh the vehicle in as-driven form. Vehicle weight has a meaningful impact on the cam specifications required. Additionally, determine what the final drive gear ratio is and at what RPM the engine will see most of its use. A cam whose intended operating range does not fall within the actual range the vehicle typically operates in will result in poor performance.
Determine the airflow needs and characteristics of the engine. Cylinder head and intake system airflow have the greatest impact on where an engine makes its power most efficiently. Very large-port, high flow heads work best at high RPM, and need a cam that is designed for that RPM range to make the most power. Conversely, smaller heads produce more low-RPM torque and less high RPM horsepower. These heads should have a camshaft with a more conservative design.
Contact a camshaft company's technical help desk by phone. Provide them with as much information possible -- as discovered above -- for recommendations of suitable cams. Alternately, consult with their online catalogs: these product guides typically provide descriptions of cam requirements and best applications.
