Flat Tappet Cams vs. Roller Cams
Manufacturers and racers have used flat tappet camshaft systems over the years with great success. However, manufacturers and racers favor roller tappet cams (when rules permit their use) because roller cam designs have distinct advantages over flat tappet designs:
Sliding frictional forces are higher than rolling frictional forces. Therefore, a roller cam takes less horsepower to turn and generally does not wear out as quickly. An added benefit is that roller tappets do not require replacement when changing cams. And, if "pop-up" solid roller tappets are used (such as P/N 72400LUN), the camshaft can be swapped without removing the intake manifold.
If a cam profile has more "area under the curve," it has the potential to make more power. Roller profiles can be more "aggressive" and accelerate the tappet more than a flat tappet profile.
Flat tappet profiles can only be shaped up to the point where the tappet "digs into" the profile. Roller tappet profiles are not limited by this condition-so much that even "inverted radius" profiles are possible.
This benefits engine performance in two ways: more tappet lift can be achieved without the added duration that would normally be required to "ramp up" a flat tappet to the added lift-making the lift curve more "pointy"; the lift curve can be made "broader" without increasing lift. Of course, both of these benefits can be combined to create a profile that can easily outperform flat tappet cams.
Unfortunately, roller camshaft systems cost more than a flat tappet cam and lifters. Much of the added cost is due to the lifters. However, roller tappets can be re-used, where as flat tappets cannot be re-used. If you tear down your engines frequently, the rollers can be used over and over again provided they are not damaged or show signs of wear.