Hydraulic-roller lifters like...
Hydraulic-roller lifters like these from Comp Cams allow for a more aggressive lobe profile with more area under the curve than a similar flat-tappet, improving idle quality and throttle response without compromising valvetrain life.
Rock-Solid Roller Solutions
Q. What typical advantages do mechanical-roller camshafts offer, and what types of modifications are necessary for installation into a Pontiac V-8?
A. Knowing that mechanical flat-tappet camshafts typically offer improved performance over hydraulic units at the cost of additional noise and possible maintenance, we wondered if the situation was similar between mechanical- (or solid-) roller camshafts and their hydraulic counterparts. David Butler of Butler Performance in Leoma, Tennessee, says, "Solid-rollers produce the most horsepower and torque of any camshaft design because they are the most efficient. They simply open and close the valves at a quicker rate, but they aren't for every application."
Mechanical-roller camshafts are typically associated with race-only applications, but street versions are available from a variety of manufacturers. "Hydraulic-rollers have lessened the use of solid-rollers on the street," says Butler. "But in general, solid-roller cams are noisy because of the valve lash, and the aggressive lobe profile takes a toll on a number of parts. Valvespring pressure is very high, so this along with the necessary valve lash puts stress on the roller bearings of the solid lifter, and the heat generated within the valvesprings limits their life."
Butler says that since each application is different, he cannot offer a blanket suggestion on street-roller-component longevity. "It all depends on the brand, how aggressive the lobes are, and how much the Pontiac is driven. We still suggest checking lash settings every few weeks with stud-mounted rockers and once a month with shaft-mounted rockers." He does, however, suggest racers routinely check valve-lash settings after every couple events.
Installing a mechanical-roller camshaft into a traditional Pontiac block doesn't require any major modifications. Butler says, "We found very few applications that mandate roller-cam bearings. Stock bearings are typically fine if they've been fitted properly, but we do highly recommend lifter-bore braces in race applications." He adds, "Oil restrictors of some type are required, especially with aftermarket aluminum heads. We install lifter-bore restrictors in race-only engines but use restricted pushrods in street applications. This supplies the entire roller lifter with maximum oil for added life.
"We typically use a billet timing set and a new stock-replacement thrust plate and fuel pump eccentric," says Butler. "If we're not using a mechanical fuel pump, we'll install a stepped washer in its place. On the opposite end, we use BOP's composite distributor gear, also adding positive oiling to it. Longer pushrods are needed because of pushrod-cup height, the cam's base circle diameter, and because we typically run longer valves to achieve correct spring pressure. We recommend a rocker stud girdle with cast-iron heads, but smaller street applications can get away without one. We do require a girdle when combining an aluminum head with any type of solid-roller, though."
Cam Company Comments
Q.As a camshaft manufacturer, has your company noticed any distinct changes in industry trends, and are there any major contributing factors?
A.After hearing engine builders' perspectives on the advantages of the specific types of camshafts, we approached camshaft-manufacturing giant Comp Cams in Memphis, Tennessee, for the company's perspective on the current state of the valvetrain market and the direction of its future.