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Hot Rod Magazine - What You Need To Know About Valvesprings

Discussion in 'COMP Cams Technical Reference Articles' started by jjamros, Feb 2, 2011.

  1. jjamros

    jjamros Guest

    There's A Lot More To Valvesprings Than Seat And Open Pressures. Here's What You Need To Know.

    For many years camshaft technology was limited not by any lack of knowledge on the part of lobe profilers but by valvespring technology that just wasn't up to stabilizing aggressive lobe designs. But within the last 10 years, spring material and design improvements have evolved that-in conjunction with ever-lighter valvetrains-enable the potential of modern cam lobe profiles and high-flowing cylinder heads to be fully realized. Today, we have more spring choices than ever, but that also means it's easier to go down the wrong path or to very quickly get confused on all the intricacies of installing and setting up valvesprings. To answer the most basic but often misunderstood questions about valvesprings, HOT ROD consulted with a variety of experts, including Billy Godbold (Comp Cams), Joe Sherman (Joe Sherman Racing), Judson Massingill (School of Automotive Machinists/SAM), Ken Crocie (H-O Enterprises), Ken Duttweiler (Duttweiler Performance), and Steve Brulé (Westech Performance).

    New Tech, New Thinking
    Typical springs and retainers used in current high-performance and racing engines include (from left) a modern single beehive spring, a dual spring, a dual spring with damper, and a triple spring. Duals with dampers are on their way out. The preferred solution is a dual in which the inner spring retains some damper-like properties due to its tight interference fit.​
    As applied to high-performance work, the valvespring's principal function is preventing valve float, defined by Godbold as "the limit speed of the valve where the spring is no longer controlling motion." The more radical the cam, the more spring you need. Traditionally, spring engineers made stiffer springs by using better materials, increasing the number of coils, and/or increasing the size of the coils. As cams became more aggressive, springs got larger, heavier, and had more elements added: Duals replaced singles, triples replaced duals. Eventually this became counterproductive because a significant portion of the big spring's higher pressure was wasted trying to control its own weight.

    In the last 10 years, new materials and configurations have been developed that allow smaller springs to control the valve with larger cams. Even on the high end, the new-gen doubles can often replace triples. As Duttweiler puts it, "An inner spring on a traditional triple assembly adds a good portion of its weight to the spring mass-as much as 40 grams more. We often remove the inner on a triple and don't lose anything."

    New wire shapes and configurations have also changed spring selection. Coil spring wire used to be round; now (although more costly), some springs use ovate (oval-shaped) wire. An ovate wire gives you more spring in a given amount of space, which means that at the same installed height, an ovate wire can handle more lift than an old-school round-wire spring before stacking solid.

    Some new springs no longer retain a constant top to bottom diameter. Of particular interest to street high-performance and entry-level street/strip bracket racers, the beehive spring has a narrow top, expanding to a wider bottom. This type of spring is used in many new production engines and is now available for older engines, too. They save significant weight over constant-diameter springs for an equivalent application: The spring itself is lighter, plus its small-diameter top permits a very small and lightweight retainer without going to exotic retainer materials. Depending on whom you talk to, on the top end, the beehive's mass reduction is worth anywhere from 200 rpm to (on a hydraulic roller-cammed big-block Chevy) as much as 1,000 rpm.

    Click here to read the full article on the Hot Rod website, or purchase the November, 2010 issue of Hot Rod.

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