The valve spring is frequently one of the most overlooked and unsung components within an engine, yet fewer components within an engine are more highly stressed and absolutely crucial to engine performance than the valve spring. What appears to be an extremely simple engine component is actually one the most highly complex pieces of equipment in a modern racing engine whether that engine is being used on the drag strip, road course, dirt oval, or even a maximum effort street/strip machine.
With terms and specifications to consider like coil bind, installed height, spring rate, active mass, natural frequency, etc., selecting and then properly installing the correct valve spring for a given application can quickly become an overwhelming task. Fortunately there are manufacturers such as Manley Performance Products who fearlessly tackle the sometimes daunting challenge of how to build a better mouse trap in order to provide racers with only the very best of products not only in terms of performance, but also in terms of durability, longevity, and reliability.
Mastering all of these characteristics and refining them into one complete package is difficult at best within the world of valvetrain technology. Yet through relentless research, design, testing, and the use of super-premium raw materials combined with superior manufacturing ability over 48 years of operation Manley Performance has risen to the top as one of the aftermarket industry’s upper-echelon valve spring and valvetrain component manufacturers.
The Need For Increased Performance
As racer demand increased over the years for more horsepower, more torque, more RPM, and more reliability, the gap between camshaft technology and valve spring technology became seemingly larger and larger. With cam grinders constantly pushing the envelope by producing more and more radical lobe designs, valvetrain components are consistently being punished far beyond conventional limits.
Trip Manley notes, “Valve springs are high stressed in engines. People need to understand that there are always limits. The springs limit engine builders and cam designers, and a better spring allows cam guys to do more with the cam. Cam technology keeps ratcheting up, and springs are the control.”
With seemingly square-lobe camshafts being produced today that provide tappet acceleration rates previously unheard of and valvetrain motion so aggressive it can turn the stoutest of pushrods into a spaghetti noodle, the need for superior valve spring technology combined with unsurpassed durability is greater than ever before.
Enter the Manley NexTek series of valve springs.
When engineering the “Next Technology” in valve springs, Manley had a goal to provide a solution to control the valve train without suffering load loss. Ultimately, they wanted their customers to have a valve spring available that provided control, would not lose load, and that would not break.
This quest to build a superior valve spring all started with a desire to help Top Fuel and Top Alcohol teams gain a competitive edge by reliably increasing RPM capability while reducing component wear and breakage.
Construction Methods And Technology
Valve springs are high stressed in engines. People need to understand that there are always limits. ~ Trip Manley, Manley Performance
Once this superior material was selected Manley used computer-aided modeling to come up with a working model that significantly reduced valve bounce and separation between the valve gear components including the valve spring, retainer, and locks.
The manufacturing process proved extremely critical in the development of the NexTek series of valve springs. “The processing and heat treat and coiling makes the difference,” says Manley.
Once the round wire stock has been coiled into an actual valve spring, each end of the spring undergoes a unique grinding process in order the create the flat surface that allow the spring to properly fit the retainer as well as the spring pocket that is machined into the cylinder head. Extra tip thickness machined in during the construction process effectively eliminates breakage associated with the overload conditions generated at the thin area of the tips where the spring has been ground flat.
Additional care is exercised during the grinding process to maintain a “square” and parallel valve spring in relation the valve stem. By maintaining meticulous flatness to each open end of the valve spring, Manley insures that each NexTek spring provides the maximum reduction of side loading possible in both the valve stem as well as the valve guide in the cylinder head.
After finish-grinding has been completed, the valve springs undergo a special shot-peen and multi-step surface enhancement process. This process is performed to military-grade specifications in order to insure absolute maximum fatigue resistance within the metal. This step of manufacturing provides a smooth, dense, and tightly compacted surface on the outermost portion of the material, effectively eliminating stress risers on the surface of the metal that could lead to premature micro fissures and cracks.
Manley utilizes a proprietary heat treating process that involves multiple steps to properly heat and then quench the valve springs as part of final manufacturing. This unique process contributes to a minimization of load loss as the valve spring is continually heat- and duty-cycled.
Friction And Weight Reduction
In an effort to reduce friction and overall spring mass Manley eliminated the damper from the majority of the NexTek valve springs. An additional side benefit of damper removal is significantly reduced wear in the valve spring retainer.
Further efforts to reduce friction and heat generated during operation involve carefully monitoring the fit between the inner and outer valve springs. Each dual and triple valve spring assembly is carefully fitted and checked. Each valve spring is uniquely fitted to its overall assembly rather than resorting to a “one size fits all” mentality in manufacturing. Not only does the valve spring assembly run cooler with reduced overall friction, but harmonic dampening within the spring assembly is also maximized. All of this adds up to dramatically improved valve spring longevity.
Reducing weight within the valve train while maintaining maximum load has always been an extremely effective method for maximizing the RPM ceiling, gaining horsepower and torque, all while significantly improving valve train longevity and durability.
As an example, Manley’s popular 221460 light weight dual drag race valve spring as commonly found on alcohol Funny Car engines typically weighs 154 grams, while a typical triple valve spring running at similar loads weighs in at a significantly higher 195 grams.
Multiply this mass by the elevated RPM levels typically observed in such an engine and you can quickly see that the load at the rocker tip is exponentially higher with the heavier valve spring! All of this extra weight adds up to increased load and wear within the valve train without the benefit of increased RPM potential or improved performance.
In an effort to further reduce valve train mass, some racers have tried running valve springs manufactured from titanium. However, Trip Manley spoke to this point stating that, “Titanium springs break and really shatter. Metal goes through the engine. There’s no reason for breakage because then there’s no consistency. Steel springs are more consistent. You will start to see them lose load before breakage.”
When it comes to selecting valve springs based on overall spring weight, “There’s really no go-to formula. But in general you want the highest natural frequency and the lowest possible mass. That goes back to what we said before about dual springs replacing triples, and a single spring replacing a dual if the lift allows it and it’s not too highly stressed,” says Manley’s Michael Tokarchik.
Dual Spring Advantages
Manley has witnessed multiple drag racing markets such as Top Fuel, Top Alcohol, and Pro Mod (among others) trending back towards the use of dual valve springs instead of heavier and less efficient triple valve springs. While these smaller diameter high pressure dual springs are more difficult to manufacture, the extra effort pays off with big dividends including:
• Higher natural frequency allowing for higher RPM potential while maintaining improved spring stability
• Reduction of active mass resulting in less fatigue and wear within the spring while also aiding in frequency
• Reduction of heat and friction which contributes to significantly reduced load loss
• Reduction in overall spring weight which contributes to increase in overall RPM potential
• Smaller outside diameter allows use of lighter weight retainers which, again, reduces stress in the valve train while contributing to increase in overall RPM potential
Another area where large gains in valve spring longevity can be realized is in paying close attention to coil bind. Coil bind is a condition in which the maximum lift of the valve exceeds the maximum allowable compressed height of the valve spring before the spring coils contact each other and create a bind. Running a valve spring in a condition where it has reached coil bind is going to instantly create very destructive forces within the valve train.
However, running a valve spring in a condition where it has excessive clearance between the spring coils at maximum valve lift can also contribute to surprisingly destructive forces being generated within the valve train, especially in the valve spring itself.
Classic engine building 101 typically teaches that a valve spring should maintain a bare minimum of .060-inch clearance between the spring coils at maximum valve lift, and that more clearance is usually better because additional clearance is typically thought to provide additional safety margin. However, excess clearance (typically over .100-inch) between the spring coils will allow a phenomenon known as “spring surge” to take place as the valve is being opened and closed.
In the occurrence of spring surge the middle portion of the spring coils can oscillate or “bounce” uncontrollably between the upper and lower portions of the valve spring as the valve is opening and closing. This surging motion reduces the stability of the valve spring. Reduction in spring stability can induce premature valve float.
Valve float is an extremely destructive condition where the valve spring loses the ability to control the valve motion and, consequently, the valve can slam repeatedly into the valve seat instead of closing in one smooth motion. During valve float the valve can also possibly collide with the piston during the opening and closing events, especially at elevated RPM levels. As Manley’s Bob Schmalz says, “Valves can take all the open pressure you can give them. They see the most stress in valve float.”
Even if valve float is avoided, the phenomenon of valve spring surge will almost always result in a bare minimum of prematurely broken valve springs. As such, Manley typically recommends that valve springs should be installed and run at .070-inch from coil bind when the valve is at maximum lift. In testing and experimenting with a wide range of installed heights, Manley has witnessed a Stock Eliminator engine increase its effective ceiling by 300 RPM when running the valve springs at close to coil bind.
Springs And Retainers
In addition to their vast selection of valve springs, Manley also offers a complete and comprehensive selection of ancillary valve train components to help round out a well-engineered and properly matched valve train assembly.
Lightweight options include valve spring retainers manufactured from Ti-17 and 6AL-4V premium titanium alloys, with offerings in conventional 7-degree, Super 7, and 10-degree configurations.
While titanium has long been proven as a superior lightweight material for retainers, Manley ups the ante even further with their special TensileMax steel retainers. Manufactured from a proprietary steel alloy material using a unique heat treating and impingement process, TensileMax retainers provide absolute ultimate strength, fatigue resistance, and wear resistance all while offering the same weight as standard titanium retainers. Rounding out Manley retainer offerings are conventional 4140 chrome moly steel retainers as well as premium lightweight H-13 tool steel retainers.
Manley’s valve lock offerings include 10-degree models in both premium steel and titanium alloys, Super 7 models also available in both steel and titanium, 7-degree machined steel models, and conventional 7-degree stamped steel.
The vast majority of Manley valve locks are available to fit valve stems with conventional square-cut grooves as well as Bead Loc grooves.
Of particular interest is Manley’s LocCap system. This system raises the bar significantly above antiquated lash caps by incorporating a uniquely machined valve lock that features an internal retaining groove which fits around a corresponding external lip machined into the wear cap that installs over the tip of the valve stem.
This unique design allows the wear cap to be positively retained by the valve lock, providing a superior valve lock/wear cap assembly that insures maximum strength and durability in extreme duty environments subjected to massive spring pressure and high RPM.
Manley’s premium TensileMax steel alloy is used to manufacture the LocCap system. For racers seeking the ultimate strength with minimum weight Manley also offers the unique LocCap valve locks in a high strength titanium alloy.
As one can see, there is much more going on than meets the eye when it comes to valve spring construction and function. Thanks to Manley Performance Products, the guesswork has been eliminated when it comes to what valve springs are correct for your application. We hope you enjoyed this glimpse into the seemingly simple yet staggeringly complex valve spring!