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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Chris Mays: "Rocker arms are built from several different types of aluminum and steel alloys, and each has its pros and cons. We feel that our Ultra Gold aluminum rockers are the best aluminum rockers in the industry, using the highest quality aluminum alloy and precision-sorted needle bearings for increased spring pressures and clearance for spring diameters as large as 1.650 inches. Likewise, Comp's Ultra Pro Magnum rockers are a new state-of-the-art design. These rockers are stronger than the aluminum, made of 8650 chrome-moly steel. Their design allows for larger valvespring clearance as well. They also feature a much larger trunion for even greater increases in spring pressure. The best stud-mounted rocker arms we offer are our Hi Tech stainless steel rockers. They have all of the features of the Ultra Pro Magnums plus the benefits in strength of stainless steel."

Brad Rounds: "Reducing the weight of the rocker arms is always a priority. Where the weight is concentrated in the rocker arms is just as important as the overall weight of the rockers. The lighter the rocker, the less mass the valvespring and pushrod have to accelerate, stop, and accelerate once again in the opposite direction. However, each application dictates how light of a rocker can be used. Removal of weight out by the roller tip always pays the biggest dividends, as long as the rocker is capable of handling the valvetrain loads for that application."

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Chris Mays: "Weight is a major concern for any valvetrain. The key is reducing weight without compromising strength. Comp's Ultra Pro Magnum and Hi-Tech stainless steel rockers address this issue by minimizing weight over the rocker tips in their design. These rockers keep more of the weight centralized over the trunion area where it needs to be instead of over the valve stem, in turn reducing reciprocating weight."

Feedback Loop
Brad Rounds: "Improving the quality of rocker arms is the result of constant dialogue between engine builders and T&D. When the phone rings, it is often an engine builder that would like a rocker arm with a little more ratio, a little less weight, or a cure for some fussy problem. He might also have moved the valve locations substantially and need a completely new rocker configuration. Sometimes a racer wants to add a bigger camshaft to an engine with no valvetrain adjustability at all. That happened with Vipers, the Ford mod engines, and even the GM LS-series small-block. We continually tailor rocker arm assemblies to an engine builder's specific needs. Also, lots of engine builders want something a little bit different from their competition, and we are happy to oblige."

Valvetrain Stability
Chris Mays: "With motors turning higher and higher rpm these days, valvespring technology has improved dramatically. Rocker arms play a big role in overall valvetrain stability, and have evolved right along with the rest of the valvetrain. At higher engine speeds, rocker stability and strength is our primary concern. Rockers do flex, so as engine rpm increases along with the dynamics associated with solid or roller cams, the stronger the rocker the better. This yields more precise valve actuation. Our Hi-Tech stainless steel rockers are the strongest stud-mount rockers we offer. Shaft-mount rockers offer the most stability because by removing the rocker stud they eliminate the highest flex point."

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Rocker Ratio
Chris Mays: "Some engine combinations utilize lots of lobe lift with a relatively conservative rocker arm ratio, while others feature conservative lobe lift and a very aggressive rocker arm ratio. One method isn't necessarily better than the other, and there is a time and place for each. Adding the acceleration speed with the rocker is easier on harmonics and valvetrain stability in relation to rpm. With a higher ratio, the acceleration is in the rocker, so we can make the cam lobe gentler in ramp design. High ratios can be used to open the valve off the seat more quickly, and lower ratios can be used to stabilize a valvetrain that is out of control."


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