Rocker Arm Design - CHP How It Works

With The Help Of Comp Cams And T&D, We Break Down The Intricacies Of Rocker Arm Design

Stephen Kim Jun 22, 2010 0 Comment(s)
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Race Engineering
Brad Rounds: "NASCAR has been the high-water mark in rocker arm R&D for quite some time. If a component can be built to stand up to its rigors, it will more than likely be over-engineered for anything else. The top NASCAR teams continue to experiment to achieve ever-loftier power numbers in hopes of gaining slight advantages over their competition within very tight rules parameters. If they ask for a lighter rocker arm with a little more ratio, we try to give it to them. While extra stiffness and less mass are both desired features, longevity is a key factor. If the rocker arm will last through all the laps of tuning, practice, the race itself, and the post-race celebratory meltdown, T&D makes teams smile. As for whether or not this type of technology will trickle down into the sportsman level, the answer is both yes and no. T&D builds a very high-quality product, so while newer steel rocker arms have trickled down into more grassroots race series, the T&D rocker systems have not become less costly to manufacture. However, many teams have reported that they are getting three to four times the longevity with our steel rockers, so they've actually saved money in the long run."

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Stamped Rockers
Chris Mays: "Stamped steel rocker arms represent the most basic of rocker design, but are still suitable for some engine builds. Many circle track racing classes require stamped steel rockers. Maximum lift and valvespring pressure are the two biggest limitations. A good rule of thumb is that you shouldn't exceed 0.500-inch lift and 350 pounds of open pressure with stamped rockers. In trying to run more aggressive solid cams, this has been a challenge. Comp now offers long-slot nitrided stamped steel rockers for increased lift and spring pressures."

Brad Rounds: "Stud-mount rockers have been around since the early '60s, and on the surface, look like relative bargains. Although you can pick up a set of stud-mount rockers for $300, factor in the costs of high-tensile strength screw-in studs, guideplates, and stud girdles and the total is closer to $600. That $600 buys a box full of headaches, including 2-hour valve-adjusting sessions and lash settings that move when the stud girdle is reinstalled. Shaft-mount rockers don't make horsepower in and of themselves, but they allow the engine builder to make more power by providing a stable, high-rpm valvetrain platform to work from. For the absolute ultimate in horsepower and high-rpm stability, shaft roller rockers are a must. In addition to reducing flex, they also offer greater flexibility in offsetting the rocker arms for different head and valve configurations. While shaft rockers are usually associated with race motors, today's street motors are turning lots of rpm, and we saw a gap in the market at the sportsman level. This need has now been filled with the release of T&D's new SportComp series shaft roller rockers which list for $800. T&D has streamlined the manufacturing techniques of its most popular small- and big-block Chevrolet rocker sets while maintaining the integrity of its unique bearing and adjuster sizes. The end result is the new T&D SportComp shaft roller rocker, a high-quality shaft roller rocker set priced just slightly more than complete stud-mounted rocker systems. Of course, they are available in standard offsets and ratios."

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Chris Mays: "Shaft-mount rockers have become more affordable in recent years, but stud-mount rockers have proven themselves in high-rpm applications as well. We typically recommend shaft-mount rockers for high-rpm applications that turn in excess of 7,500. Extensive Spintron testing has shown this is the rpm where you will start to have more stud flex with stud-mount rockers. However, with 7/16-inch studs and a stud girdle, you can come pretty close to the performance of a shaft-mount setup with stud-mount rockers."


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