What we did
Examined the factors in selecting a performance camshaft
Picking a cam that matches your goals and your engine combo is crucial for performance and enjoyment.
From $100 for a hydraulic flat-tappet to $700 for a hydraulic roller
It's usually the first choice made when swapping cams, and there are four options to choose from: hydraulic flat-tappet, hydraulic roller, solid flat-tappet, and solid roller. We've listed the types in order of increasing power potential, but each has advantages and disadvantages. A roller cam's greatest benefit is that its frictional forces are less than those created by the sliding action of a flat-tappet cam, which frees up some horsepower. Another advantage is that, for the most part, roller profiles can be more aggressive, employing more lift given a particular duration. On the other hand, a flat-tappet cam actually has greater initial acceleration, meaning it will attain higher lift more quickly than a roller cam, before the roller reaches its maximum velocity--which means running a flat-tappet setup can actually be the better choice when running a cam with short duration figures. As we've said throughout, it's all about choosing what works best with your combo to meet your goals.
They're inexpensive, they don't require any adjustment since engine oil pressure maintains preload against the pushrod, via a spring-loaded plunger, and they run quieter than mechanical lifters. On the other hand, they often perform poorly at higher rpm due to an inability to bleed down excessive oil pressure.
This type of tappet has been used in OEM small-blocks for the past 20 years. The roller design allows for more aggressive lobe profiles, along with the self adjustability and quiet operation of hydraulic lifters. These lifters are constantly improved but can also suffer from high-rpm limitations. In general, these cams are the most expensive, especially when springing for a retrofit cam and lifter set for an older block.
Also called a solid tappet, since it provides a solid link between the cam lobe and the pushrod, this is about as basic as it gets and is only slightly more expensive than a hydraulic flat-tappet system. These cams will rev higher than hydraulic cams but tend to be noisier. They also require a valve lash setting to account for expansion as the engine heats up.
The best of both worlds, this type of lifter allows for the more aggressive lobe designs of a roller setup along with high-rpm operation, thanks to its solid body design. It also requires a lash setting that must be periodically readjusted. A retrofit mechanical roller costs less than a similar hydraulic setup but is still quite a bit more expensive than a flat-tappet arrangement.
According to Knight, you can compare similar hydraulic and solid cams by using an 8-degree cross-reference figure. For example, a hydraulic cam with 222 degrees duration at 0.050 equals a solid cam with 230 degrees duration at 0.050.
Selecting what type of cam to use may be the first decision usually made, but choosing the cam's duration figures--the amount of time the valves are held open--is arguably the most important. "Duration and lobe separation pretty much control the engine's basic rpm range," says Knight. "Lift controls how much power you make in that rpm range."