Hydraulic rollers eliminate the need for cam break-in and the potential for lobe/lifter fa
Since the solid’s main benefit is stability at high rpm, this type of a cam is best used where a high-rpm engine is the goal. As a flat tappet, the limitations on spring load capacity are similar to the hydraulic flat, which is rather contrary to the goal of maximizing rpm. Spring selection and valvetrain setup is critical when trying to make the most of a flat tappet solid. If the displacement, cylinder heads, induction, and rotating assembly are capable of supporting the engine into the 7,000-plus rpm range, a solid is a viable option. On the other hand, if the engine combination is destined to run out of rpm capacity and airflow at 5,500 rpm, a solid will be of negligible benefit versus a hydraulic.
The hydraulic roller has taken over as the most common OEM cam configuration, using an internal adjustment mechanism and a roller follower. It shares the hydraulic flat’s characteristics of quiet operation, no maintenance, and compatibility with a low-cost, non-adjustable valvetrain.
Side by side, a roller cam’s lobes (left) seem much brawnier and beefier than those of a f
The primary benefit of this arrangement is a higher load bearing capability at the lobe/lifter interface. Flat tappet cams are subject to failure here, with disastrous results. The roller follower’s higher load capacity virtually eliminates these failures, and that is reason enough for many builders to favor this cam configuration. A hydraulic roller allows substantially higher spring loads than are practical with a flat tappet, lending to higher lift while maintaining valvetrain control. The geometry of a roller follower and cam lobe allows higher velocity than a flat tappet, so the lift curve can be designed with longer duration in the upper lift ranges, enhancing power production.
High-rpm stability and related drawbacks of the hydraulic roller are similar to those of a hydraulic flat tappet. The heavier lifter weight can make this more acute, however, some higher valvespring load capacity helps here. For extended rpm capability, aftermarket manufacturers offer limited-travel hydraulic roller lifters for popular applications, which restrict the lifter’s internal plunger travel to improve stability. With all of the hydraulic roller’s advantages it is an excellent choice for street performance, though cost scales up quickly in retrofit applications.
Solid roller cams come into their own at the extremes of engine rpm, lift, and valvespring
In an automotive performance application, the solid roller combines the load bearing capacity of a roller follower with the inherent stability of a solid lifter body. The result is the ability to run very aggressive, high-lift lobes and the substantial spring loads necessary for high-rpm control. For all-out power production and rpm capacity, the solid roller is the king, however, in the wrong application, a solid roller is a poor choice.
A solid roller comes with bragging rights, but experience has shown that this cam configuration offers questionable long-term durability in a true street application. The most common failure point is at the follower wheel’s needle bearings, and when they let go, serious engine damage typically follows. New, higher quality lifters with improved materials and direct oil feed to the bearings are the industry’s answer. Before taking the plunge into a solid roller, the first question you should ask yourself is whether the engine truly needs one. If very high rpm, extreme valve lift, and the requisite high spring loads are all part of the plan, a solid roller is the right choice. If not, other cam options may meet your performance needs, generally with greater durability and at a much lower cost.