Hydraulic Roller Cams

By Jeff Burk
4/7/03

There's an old joke in the pits that goes something like "How do you know when a motor is in a bracket racer's car? If the valve cover nuts are rusted and the valve cover is dusty."

The point of the joke is that bracket racers simply don't have time to do a lot of maintenance between rounds. Cooling the engine and trans, refueling and perhaps a few adjustments to the throttle stop and delay box are about all they have time for, especially if it is a six, seven or even eight round affair. They especially don't want to be forced to take the valve covers off and adjust the valve lash or check springs or any of those things that Pro and some class racers have to do as a matter of course.

So, both weekend warriors and professional bracket racers are buying engines built to deliver the power they need without being run on the ragged edge every pass. They generally are buying 500-600 inch engines that make power at 8,000 rpm or less and require freshening once a year at most.

In order to deliver that kind of power and performance, engine builders have had to develop engines that deliver the torque and horsepower the racers want and yet are reliable.

One area in the engine that has been the subject of much R&D in an effort to deliver parts that are "bulletproof" is the valvetrain. Roller cams, lifters, rocker arms and high pressure springs have long been the choice of engine builders when it comes to building engines that are both reliable and powerful. Builders know that in order to make power at higher rpm ranges or with smaller motors, the use of mechanical "roller" camshafts, lifters and springs has been required. Those pieces, however, are expensive to buy and replace, and re quire regular maintenance by the racer.

DEFINITIONS

Just what is a "roller" camshaft and why is it a desirable item to have in a high performance engine? The term roller actually doesn't apply to the camshaft itself but rather to the lifters and the rocker arms. A "flat tappet" camshaft's lifter is a solid cylinder of metal that sits directly on the surface of the cam lobe and actuates the push rod and the rocker arm. A solid or hydraulic lifter combined with a standard no-roller rocker arm create more heat and drag in the engine because of friction.

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