Sep 15 , 2023
Camshafts: Hydraulic vs. Roller
You may have heard of guys using roller cams in the racing and hot rod worlds. The cam itself does not have a "roller" function; those are the lifters that people are referring to when they talk about a camshaft. The cam itself is a solid steel bar that’s precisely machined with ramps (or lobes) that in turn operate a set of lifters. How they are machined and operate the lifters (which are either solid steel, hydraulically operated, or with roller tips) is where the nomenclature comes in. The cam is nothing more than a stick that spins around and operates the lifters, which in turn operate the rest of the valvetrain.
A camshaft is much more important than that previous statement just said, however, and how it is machined has an enormous effect on an engine’s character. It is generally accepted these days that a roller cam should always be used in a modern engine, since the function of roller lifters means far less frictional loss and therefore more power. But beyond frictional loss, a roller cam actuates the valves in a much quicker motion for dramatically more power. The advantage of a solid cam is simplicity and lower cost, whereas the advantage of a hydraulic cam (lifter) is that it is self-adjustable. A solid cam, be it a flat tappet or roller, has its lash set, and that’s done, whereas a hydraulic lifter has a hydraulic plunger that takes up lash automatically and holds that adjustment for a long time. The disadvantage of a hydraulic cam is weight—the oil and plunger mechanism weigh more than the mechanical pieces of a solid or roller cam, and weight is always your enemy in the valvetrain.
We really could write an entire book on the subject (and a few have!). But when you’re looking for an inexpensive camshaft to run in an engine and one that doesn’t need a lot of maintenance, choose a hydraulic cam. That’s what most passenger vehicles have had since the 1950s, because it works, is pretty cheap, and rarely fails. In the 1980s, factories began using roller cams due to their better durability in performance applications. If you want maximum power and the hip thing at cruise night (even though nobody will know by looking at the car), pick a roller cam. If you want the distinctive "tick" sound of a hot rod, go with a solid cam. The choice is 100% up to your desires, but it can affect the car in more ways than just noise. A cam can require a lot of thought, and it should. The Cathedral Port Cam in our featured image has a vast list of applications. While you shop, take a look at our Ford crate engines too!