PRI Magazine — May 2013
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Valve Springs & Rocker Arms: Vital Parts In The Engine Package
John F. Katz

The rapid development of new heads is driving demand for a wider range of shelf-stock rocker arms, as well as a growing market for custom pieces. Plus, changes are aplenty in valve springs, report manufacturers.

Right now the rocker arm business, well, rocks. The rapid development of new heads is driving demand for a wider range of shelf-stock parts, as well as a burgeoning market for custom pieces.

“Our fastest-growing business right now is in rocker arms,” reported Kerry Novak of Crower Cams & Equipment, San Diego, California, “especially shaft systems, because the cylinder head manufacturers are releasing so many new designs that have to have shaft rockers on them. So it’s a really good business right now.”

“Aftermarket head companies have made improvements that affect how the rockers work,” added Randy Becker Jr. Of Harland Sharp, Strongsville, Ohio, “and most aftermarket heads benefit from a head-specific rocker”—both in terms of performance and longevity.

At the same time—and not surprisingly— “The constant quest to be competitive translates into more aggressive cam profiles, higher valve spring loads, and higher rpm,” noted Gordon Johnstone of Scorpion Racing Products, Ocala, Florida, “which, of course, increases the demand on the entire valvetrain. The trend is toward the highest- grade raw materials and latest analytical technology and design—resulting in the strongest and lightest products, with the highest level of precision and tightest possible tolerances.”
“Even in a stable valvetrain,” added Brian Reese of Comp Cams, Memphis, Tennessee, “the loads and forces on rocker arms are very high. When the valvetrain exceeds its stable operating range, the resulting out-of-control impacts can cause almost immediate rocker arm failure.” Ideally, rocker arm design should “optimize the moment of inertia without compromising rigidity and strength—balancing the emphases on mass, stiffness and durability. There’s a vast difference between drawing a rocker arm that fits, and thoroughly engineering a rocker arm design that performs properly and lasts without failure.”

In short, the market is not only demanding more rocker arms, but also greater variety, enhanced durability, and more precision engineering. And much the same can be said for valve springs as well—where “longevity is increasingly challenged by ever-higher valve lifts, accelerations and spring pressures,” said
Willy Tagliavini of Supertech Performance, San Jose, California. “We are continually adjusting to new applications.” But first, let’s focus on rocker arms.

Rockers Around the Clock

As we noted at the start, demand for both more parts and new part numbers is positively exploding. “Production is rolling non-stop,” said Novak. “We’ve partnered with Brodix, Dart, AFR and All Pro to develop brand-new shaft rocker systems—in aluminum, stainless steel, and now we’re even using 4340 chromoly billet. We just developed a brand-new system for the new Brodix LS head, and now we’re working on their new big block Chevy head. They send us three heads, and as soon as we’re done they send us three more. Right this minute we’re expecting a new head from Dart that we haven’t yet seen. It’s a constant flow of new cylinder heads, and it changes every day.”

The choice of material, Novak added, is based “on the individual application: How much rpm? How much horsepower? How much boost?”

At Jesel of Lakewood, New Jersey, “our biggest strides have been in the design and development of our steel rocker arms,” said Rob Remesi, “which are custom-tailored to specific engine builds and overseen by our Custom Shop. Our steel rockers saw great success in 2012, with championships in NHRA Top Fuel, Funny Car and Pro Stock classes, as well as the points championship in World of Outlaws sprint cars. Wherever longevity has become an issue, we recommend our Pro Steel rocker bodies. Most of our endurance-racing customers are now running steel rockers, also. Any aluminum piece will fatigue in time, whereas the life of an equivalent component made of steel is almost infinite.”

Jesel does offer aluminum rockers, which are shot-peened to “induce an even compressive stress layer in the surface of the body. This increases the resistance to fatigue failure by relieving tensile stresses from the machining processes and replaces them with beneficial compressive stresses.” Both Jesel’s Sportsman Series and Pro Series aluminum shaft rockers have been expanded to include new applications for 2013. “Typically,” Remesi continued, “our standard Pro Series rockers are designed for naturally aspirated engines with open spring pressures under 1000 pounds. Engines with high cylinder pressures, such as Pro Mod nitrous or supercharged applications, require a steel exhaust rocker. Any engine running open spring pressures over 1000 pounds should be using nose rollers with needle bearings.”

The LS Influence

Another factor contributing to the growth of aftermarket rocker arms is the increasing numbers of GM LS engines being built for racing. Some of these are shaft systems; others are upgrades to the stock system, where shaft-style rocker bodies articulate on individual trunnions that straddle individual mounting studs. “At the upper end,” noted John Steely of Howards Cams, Oshkosh, Wisconsin, “we would only use or recommend a shaft rocker system to maintain valvetrain stability.” But premium stud-mounted rockers will work well in a wide variety of applications. “Our supplier builds our roller rocker arms with matched bearings and a strong body profile. They work in any stud-mount situation with minimal flex; and they come with a lifetime warranty to the original purchaser.” Scorpion has released new roller rockers for the LS3 and L-92. “This is a direct bolt-on kit,” said Johnstone, “meaning absolutely no machining is required—nor are valve-cover spacers.” Stock pushrods, guide plates and rocker studs can also be retained. The new Scorpion rockers are available in ratios of 1. 7 and 1.8 for intake and exhaust, or in a 1.7 intake/1.8 exhaust combination, all with an eight mm pedestal mount.

Yella Terra of Melbourne, Victoria, Australia, is expanding its line of widebody Platinum Series shaft-mount rockers “for race applications where radical lobe profiles and severe spring pressures come into play,” said Roger Vinci. This includes applications “for most new aftermarket LS3 and LS7 cylinder heads, in several ratios. These new rockers have larger bolts and can withstand spring pressures up to 1000 pounds.” All of its Platinum Series rockers have large trunnions and are equipped with an integrated circlip to retain the nose wheel axle. Unique 8620 steel pushrod cups allow pressurized oil to flow around the pushrod tip at all times for longevity. Platinum series rockers are available in non-adjustable and fully adjustable configurations. Additionally, Yella Terra has also released new race-grade rockers for big block Chevrolet and Ford applications.

“The LS market is already huge right now, and growing with new aftermarket products and continuing development at the OE level,” confirmed Shane Pochon of Lunati, Olive Branch, Mississippi. “Like the big block Chevy, the stock rocker ratio for the LS is 1.7, and that means valve lifts are higher. Interestingly, we’re seeing customers who want more horsepower but also good fuel economy in the 2000–2500 rpm range of their daily-driver vehicles. They’re asking for valve lifts in the .700- inch range, but with very mild duration, typically 215–220 at .050-inch lobe lift. It can be done with a very aggressive cam lobe profile in a custom grind, but with a trade-off in valvetrain wear and tear. Because these are typically daily driver cars or trucks, most of these people won’t tolerate this accelerated wear.”

Harland Sharp is now developing new LS1 rockers for heavy-duty applications. “We are leaving more aluminum on the rocker body,” Becker said, “and changing the slot design for increased strength. We have also developed a smaller pushrod seat that removes less material, also increasing strength.”

Additionally, Harland Sharp has “finished development and testing of our new D-Force line of diesel rocker arms”—with applications for the GM 6.5, Cummins 12 valve and Cummins 24 valve. “These aluminum roller-tip rockers are for modified applications and requirement fitment by the installer,” Becker added. “The 24 valve Cummins system features a newly designed roller bridge.”

One of the newest products available from PRW Industries, Perris, California, is the GM LS3/L92 Platinum Series rocker with 1.7 ratio offset intake rockers. According to Chris Roberts, this system integrates 0.675-inch complement bearings, 0. 875-inch micro polished trunnions, 17-4 pH stainless steel full roller body and an internal oiling system to ensure proper lubrication at all engine speeds and horsepower levels. A Clean Nitron finish is added for strength and reliability.

Roberts noted that PRW’s design process for rocker arms or rocker systems is extensive. “We have to take into consideration varying valve springs pressures from smallest to largest. This is why we design our 15-5 pH Steel Alloy Platinum Series rocker to operate with spring open pressure in excess of 900 pounds (7/16- inch stud). At the same time being concerned with the mass of the rocker, critical area of attention is paid to ensure that high engine rpm can be handled without the worry of valvetrain degeneration.”

Durability today’s rocker arms have to be built tougher than ever to survive such extremes. It’s even more critical to engineer the entire valvetrain to meet the demands of the cam profile. “We’re spending a considerable amount of time on R&D efforts,” said Pochon, “and hours of Spintron testing for street-driven applications as well as all-out racing engines. The point is, whether you are looking at 2000 rpm in a street engine or 10,000 rpm in a race engine, the valvetrain components and especially the valve springs themselves must have the correct tension and travel to survive these extreme valve lifts. And that, of course, means you must have a rocker arm capable of handling the spring pressure required, and a very strong, rigid pushrod that won’t flex and destabilize the valvetrain.

“Our research has shown that the actual weight of the pushrod is of less importance in a race engine, but rocker arm design must be as light as possible, and strong enough to handle the application,” continued Pochon. “We’ve recently redesigned our Lunati Voodoo line of stud-mounted rocker arms to meet these challenges. The extruded-aluminumalloy rocker bodies have been reengineered to increase strength in high-stress areas while reducing weight. We’ve also changed the specifications of our steel alloys and heat-treat processing in trunnion assemblies and roller tips. The result is an extremely strong, lightweight, yet stiff aluminum rocker arm that is capable of handling these now common extreme spring pressures. They’re a great rocker for street performance or bracket racing.”

“Rocker arms and valve springs must be matched to the cam profile, rpm range and valvetrain weights,” Steely agreed. “Failure to do this guarantees that either the valvetrain will not perform and/or the engine will be damaged.”

“Attention to detail, along with careful planning and research go a long way toward keeping rockers and springs happy,” added Mike Schropp of Livernois Motorsports, Dearborn Heights, Michigan. “Knowing exactly what the application is, what the intended use is, and all the details that go along are critical to selecting the proper parts. The next step is preparation: setting heights, checking geometry, ensuring clearances, etc. All of these details are critical to ensure that the valvetrain will live a long and happy life.”

Comp’s new Ultra-Gold ARC aluminum stud-mount rockers “are the direct result of continuous engineering development of our original Ultra-Gold rocker. The shape of the body is an arch, the strongest shape possible, geometrically,” said reese. “The center section is channeled out to reduce mass while maintaining the full strength of the arc. Then we contour the pushrod area, cutting off unnecessary mass to improve the rocker arm’s dynamic range.” This “extra step,” Reese claims, is unique among aluminum stud rockers, as is through-the-body oiling, “providing a steady flow of cooling oil to the valve and valve spring.” Precision-ground surfaces of the axle and trunnion reduce friction and further enhance longevity.

Crane Cams of Daytona Beach, Florida, has “upgraded our Gold Race rocker arms to an aluminum alloy that’s stronger at actual operating temperatures,” said Chase Knight. “A burnished finish on bearing contact surfaces also reduces friction and increases longevity.”

Titan Speed Engineering of Ojai, California, has developed all-new rockers for the vintage Chrysler 354/392 Hemi. “Our new design uses much longer valves and valve springs,” said Bob Sanders. “The ratio is much higher also, but the rate of lift is dropped back a hair, as there is so much more travel (and airflow) available. So torque is increased throughout the rpm range and, with more spring area available, the valve springs live much longer.

“We are also working with Arias Industries to integrate this new technology into the venerable 8.3-liter Arias Hemi,” Sanders continued. Titan offers several different rocker arms for the Chrysler 354/392 and Arias 8.3 Hemi, and also for the Toyota 2TC and 3TC. “We now make three different length ball adjusters,” Sanders added, “as well as cup-type adjusters; all feature an oil hole for lubrication. We have always strived to make racing parts that you have to think about as much as you think about your front wheel bearings. We’ve done extensive failure and cycle testing, and we are always looking for the very best materials, heat treats, coatings, and—above all— design.” Titan uses only US-manufactured adjusters, fasteners and bearings.

Material selection and heat-treat procedures are the main concerns of Manton Rocker Arms, Lake Elsinore, California, when the company approaches the design of any valvetrain component, according to Noel Manton. “The rocker is very highly stressed, and if we expect the finished part to provide the durability necessary to function at high engine speeds, we must use the finest material available. Stiffness is critical, which leads us to use 4340 steel,” he said.

“Our latest addition to our product is a roller tip exhaust rocker arm,” added Manton. “We realized the need after seeing failures in the A/Fuel Dragster category. The cylinder pressure can be as high as 13,000 psi. Needless to say, the rocker arm has some work to do in an environment like that. The rocker is machined from a 2.5” x 3.00” x 5.25” piece of 4340 steel. The consistency of a salt heat-treat procedure is used to provide the strength requirements. It is polished and electroless nickel plated for corrosion protection in the nitro methane environment. The rocker is then assembled with our tool steel rollers, tool steel axle pins and tool steel adjusting screws.”

Needles or Not

CHE Precision of Newbury Park, California, continues to replace the troublesome needle bearings in LS rocker arms with simple bushings. “The rocker arm itself is excellent,” said Ed Doyle. “It’s a beautiful casting, a gorgeous little piece with a low tip weight, and up to about .550 or .600 lift. They work beautifully. But we found that the needle bearings were breaking up and failing. So we’ve solved a lot of problems by pressing out the bearing and putting in a new bushing and trunnion. We have customers who rev them up to 7000, and even a little higher, and they haven’t had any trouble.

“And after seeing how well that worked with new LS rocker arms, we started taking in old rocker arms and rebuilding them the same way,” he continued. “We’re doing a lot of business with off-road racers who buy brand new sets of rocker arms and send them to us to rebuild. And they are having much better success than they had with needle bearings, because needle bearings don’t like dirt.” CHE’s bushings are made from “a proprietary material that was engineered specifically for this application. It has very low friction, and it can stand significantly higher loads than regular brass or bronze.”

Crower, said Novak, has switched its roller tips from bearings to bushings. “And we have some racers right now with bushings in their rocker arms where they pivot on the shaft. We’ve been experimenting with that in our billet rocker arms. But you have to have oil on that bushing material. We have oil going through the rocker arm, from where it articulates on the shaft out to the axle in the roller, and then it squirts out at the tip.” But Crower is gathering data before deciding whether to replace needle bearings completely. “It’s one thing to run it on a Spintron, it’s another to put it in a race engine. We have two of our dealers running them in our race vehicles now, putting laps on them. We’ll see what happens as the season progresses.”
Valve Springs

Valve springs, as much as rocker arms, need to be engineered for a growing range of more-demanding applications.

According to Pochon, the valve springs used today have undergone great changes. “We’ve found that nothing influences the longevity of a valve spring more than the quality of the wire material and the method used in the manufacturing process for valve springs,” he said.

“Chrome-silicon steel has been a mainstay for valve spring material, and remains so today. However, there have been important advances in the material itself. For example, multiple filtration processes are now used to remove more of the impurities that can lead to product flaws and failure. New manufacturing techniques also now allow us to nitride process the chrome-silicon material. This hardens the surface of the spring wire and helps maintain the specified tension over the lifetime of the spring.” Other manufacturing improvements including shot-peening and micropolishing are used to extend valve spring life.

Lunati has expanded its line of premium Signature Series valve springs to meet the needs of race engine builders. “We now offer installed heights of up to 2.350 inches, plus larger OD wire dimensions and greater pressures in both on-theseat and open-load specs,” said Pochon.

Supertech, added Tagliavini, is “working with our wire manufacturer to obtain better quality wire, not just free from impurities, but of the optimal chemical composition and surface treatment to maximize tensile strength and fatigue life. We periodically cycle-test our springs to check fatigue life, and adjust our design and software accordingly. And we design not only the spring, but the entire spring kit for each application, adjusting every allowable dimension—diameter, installed height, etc.—to increase the fatigue life of the spring.”

Howards Cams, said Steely, has been “working with our spring suppliers on better materials and processes, not only to increase durability but also to reduce harmonic frequency issues, and to increase spring pressure with less stress.” Surface treatments and coatings can contribute to these goals. “One of our suppliers is PAC Racing Valve Springs (of Southfield, Michigan). This has allowed us to add the most up-to-date spring technologies to our product line with a minimum of lead time.”

“Our advanced superfinishing processes have increased longevity immensely,” added Reese. Among Comp’s newest valve springs is part number 26526, a superfinished dual spring specifically developed for extended life. “Instead of single stages of shot-peening and polishing,” Reese noted, “26526 undergoes proprietary multi-stage post-processing comprising progressive steps through heat treat, micro-shot, and polish.”

Knight also emphasized, “Premium materials with enhanced surfaces,” which, “along with cryogenic treatments for some materials, can provide a longer lifespan.” It’s also important to “carefully inspect each spring for surface imperfections, and for any roughness where the ends are cut and ground.”

“We’ve been testing new materials for the past year and a half,” said Bob Kamp of K-Motion Valve Springs, Lafayette, Indiana. “We’ve spiked our alloys with proprietary materials that enhance longevity and reduce heat in the wire.” Longevity is also enhanced by spring oilers, and by “proper warm-ups, maintaining proper valve adjustment, and remaining calm in the water box.”

We found other factors can influence spring life as well.

“In testing multiple-spring setups,” noted Sanders, “we have often noted stress risers and heat build-up where the springs touch each other, leading to rapid spring failure.” This is just one more reason why “there are huge benefits to spraying the springs with oil.”

New Choices, New Applications

“Most of our newer springs are engineered for the later Ford 5.0-liter Modular Coyote/Boss engines,” said Schropp, “as well as the 6.2-liter Raptor. We offer a couple of different packages for those engines that will work in a wide variety of applications.” Livernois “also offers some extended-range GM LS springs for applications that go beyond the usual street/ strip builds—allowing us to tailor specific valvetrain packages around a variety of different applications.”

Mike Downs of Trick Flow Specialties, Tallmadge, Ohio, pointed out that valve springs “are considered wear parts and must be replaced periodically to maintain performance integrity.” The company offers four new dual-spring upgrade kits for GM LS cylinder heads. “Two kits are targeted toward customers who want to keep their stock rocker arms,” Downs added. “The other two require upgraded, roller-tip rockers. All four include a choice of steel or titanium retainers, plus seals, locks, ID locators and instructions.” Trick Flow also offers “a wide range of valve springs for a huge number of combinations.” All are US-manufactured and supplied by PAC Racing Springs.