[curtis73]

The 4.0L in the truck will be designed to operate between idle and 5000 RPMs. (read my other response to your other post first if you haven't already). It will use a short duration cam to trap as much intake charge as possible at lower RPMs. That will make torque in the low RPM range which is needed to get a heavy truck and cargo moving.

The 4.0L in the race car doesn't care about low end torque. All it cares about is maximum HP because once it leaves the starting line it will never idle again. Maximum HP happens at higher RPMs, so the cam has more duration and the heads flow a lot more to support higher RPM operation. It will be spinning between 9000-12,000 RPMs all day.

On the street, a car constantly operates between idle and 5000 rpms, so it needs a cam and head combination to make power and torque in that range. A race car engine operates in a very narrow, high RPM range, so it uses a larger cam and head flow.