Valve springs, whether they’re single or dual, conical or beehive, made of round wire or ovate, are subjected to stress levels that would cause most other parts of an internal combustion engine to fall apart at the seams. Related Articles - Shop Solutions – December 2024 - Cam Bearing Breakdown - High Performance Expo Aims to Impress with Inaugural Tradeshow
These components, which work together with the camshaft to control the precise movement and timing of the engine’s valves, must compress and expand dozens of times per second. They also have to endure extreme temperatures, often exceeding 200°F. control valve
In addition, valve springs face fatigue stress from repeated compression and expansion, as well as harmonic vibration at specific frequencies. All of which highlights the importance of their precise design and construction for a properly functioning valvetrain and, by extension, a smooth-running engine.
Before these parts are released from the manufacturing floor, they must first undergo a series of tests and evaluations to ensure they can handle millions of cycles in harsh conditions. To better understand how modern springs are meeting the demands of today’s engines, we spoke with experts in street and performance valve springs for a behind-the-scenes look at testing techniques and processes.
PAC Racing Springs designs, manufactures, and sells high-performance engine valve springs, retainers, seats, and locks to customers across the globe. Known for dual drag race spring technology used in high-end drag race engines, PAC produces an extensive line of beehive springs, and is currently expanding its product range to include conical springs. The Southfield, MI-based company’s portfolio also includes specialized tools like installation height micrometers and calibration springs.
Over the years, PAC has established an elaborate dynamic testing area and metallurgical test lab that’s helped Chris Osborn and his team develop groundbreaking springs for a range of applications. Recently, he noted, they’ve made significant strides in vision systems.
“We can place a spring in front of a camera and get instant feedback on coil spacing, free lengths, and diameters at every coil section of the spring,” Osborn says. “This has greatly improved our manufacturing abilities and repeatability.”
For PAC, the development of a new valve spring typically originates from two areas. Customers may request a spring for a specific engine to control valve function at a designated lift and engine speed. The company then assesses whether an existing catalog spring is suitable, or if a custom spring needs to be created for their application. Alternatively, ideas for new springs may come from ongoing conversations with engine builders, OEMs, racers, and engineers.
“If we see new trends or engines that require springs that don’t exist, we will investigate to see if it makes sense for us to add that to our catalog,” Osborn says. “Many times, we can match our designs with our processes to offer a cost-effective solution that allows our customers to make real gains with their engines.”
Designing new valve springs requires a solid grasp of the environment they will operate in. One of the first jobs is determining available space, including the spring’s installed height, outer diameter (OD) to fit in the head, and inner diameter (ID) to accommodate guides or seals, as well as how much valve lift is planned for the engine.
“These are the main starting points,” Osborn says. “Much of the design aspects of the spring are not so much about the spring, but about what applied lifts, rpm, mass, and acceleration it will see, so the spring can provide an adequate level of control.”
On the programming side, the team uses both in-house developed applications and a few commercial software packages. While these tools can recommend a spring configuration with a specific wire size, number of coils, and diameters, they aren’t able to account for spring processing.
“It’s easy in these programs to design springs that could be built,” Osborn explains, “but as soon as you tried to press the solid or run them on an engine, they would take a severe amount of set, or fail.”
To evaluate the different aspects of wire forming, PAC utilizes a variety of equipment. Initial tests involve material assessment from wire suppliers, where the spring material is run through a tensile test machine to verify that it has the proper ultimate tensile strength (UTS). Osborn’s team also measures the reduction of area of the material fracture to determine the wire’s ductility.
“If the material lacks sufficient strength or ductility, it cannot be formed into a spring,” he says. “Actually, every spring is severely tested in its initial coiling. It takes a lot to bend a high-strength material into a circle.”
While not specific to the actual spring being tested, PAC dedicates substantial time to testing its processes. The team has methods in place to evaluate each step involved in production, including heat treating, shot peening performance, surface enhancement, and grinding. That said, every spring produced by PAC does have its own blueprint, and the tolerances for each vary depending on the customer’s requirements.
“For some low-level springs, [the customer] may not care what the solid height of the spring (coil bind height) is, whereas other people want the solid height held to within 0.005” or tighter,” Osborn says. “Generally, as the level of racing and sophistication of the engine (higher horsepower and rpm) climbs, the tighter the tolerances need to be. When these requirements are in place, the processes are held to tighter controls; and the end-of-the-line sorting is tighter as well.”
Osborn’s team routinely takes samples from a batch of springs and subjects them to cyclical fatigue testers.
“These testers will cycle the springs at any stroke we want in order to simulate what the springs will see in worst-case scenarios in an engine,” he explains. “We have a large database of how long springs should last at a given stress level for a given process. If we see something that fails early, we evaluate the failure in our metallurgical lab with equipment such as scanning electron microscopes, [as well as] X-Ray Diffraction analysis, and structure and microhardness evaluations.”
The team conducts further testing on a Spintron, which allows them to assess the spring’s performance within a specific valvetrain at speed to determine how well the spring controls valve motion.
Looking ahead, Osborn tells us there’s still room for development, especially in processing, where the team will continue working to optimize heat treat, shot peening, and surface polishing, among other areas. He cited PAC’s NanoPeen process as one example of a highly engineered surface that allows the spring to operate at elevated stresses.
“Valve springs are one of, if not the highest-stressed component in an engine,” Osborn says. “Anything we can do to improve them will improve their longevity and performance.”
Melling’s product lineup includes stock replacement and entry-level performance valve springs. The Jackson, MI-based company caters to a wide range of customers, including production engine rebuilders (PERs), camshaft manufacturers, cylinder head manufacturers, major retailers, and traditional warehouse distributors.
Among the benefits of working with engine rebuilders is “the feedback we get from their in-house failure analysis on returned core engines,” says Cale Risinger. “If the PERs are seeing issues with weak or broken OEM valve springs on core engines, we can take a look at the spring design, as well as the valvetrain as a whole, and work to develop a better spring for the application.”
On the stock replacement side, Melling’s team looks at vehicles in operation to help them decide which engines to focus on. They also consider the engines their PER customers are currently working on, or have in the pipeline, to help determine future part development.
The performance line is largely driven by customer feedback, Risinger says. Collaborating with camshaft and cylinder head manufacturing customers keeps the parties aligned and helps his team stay current on the latest market trends. Melling personnel also gather feedback from the numerous industry trade shows and racing events they attend each year.
Risinger notes that the design and testing processes for valve springs have become more detailed, advanced, accurate, and faster in recent years. Using newer, higher-tensile alloys allows his team to create lighter and more stable parts with excellent fatigue life. He also pointed to more frequent and in-depth utilization of X-Ray Diffraction for residual stress analysis, where the XRD curves provide detailed data on the compressive and tensile stresses within the spring.
“These advanced design phases and a deeper understanding of stress distribution helps us make a single higher-frequency conical or beehive spring to replace a traditional (and heavier) dual spring,” he adds. “The single part has a very high frequency and avoids any high-speed harmonic issues.”
Going from the idea stage to prototype relies on timing, material availability, and stress considerations, Risinger explains. This development process is critical to ensuring the final product meets the required specifications, and can perform as expected in real-world conditions.
Valve springs, which are subject to extreme stress levels, require a thorough approach. Initially, samples of the part will undergo extensive fatigue testing to assess their durability and identify any potential weak spots. Once these samples pass, more parts can be produced. Additional springs are then put through another round of fatigue testing to ensure the final prototype can handle the stresses of its intended application.
Diving deeper into Melling’s in-house cycle testing, Risinger explains that it’s done on a high-speed, motor-driven fatigue tester.
“Parts are installed and tested between calculated heights, where the parts will be stressed at a level of about 15% above operational stress to account for high-speed dynamics,” he says. “This takes into account the effect of operational dynamics at higher engine speeds. Live-fire engine and Spintron testing is also invaluable when it’s available.”
During fatigue testing, the first four failures are monitored and recorded. If any failures occur before reaching 10 million cycles, Risinger says, the entire batch of parts is discarded. At this point, each failure is carefully examined to confirm that it was, in fact, caused by fatigue. Depending on the findings, the part may be redesigned to reduce stress levels, or the manufacturing process may be improved to enhance compressive residual stresses.
“When parts pass the fatigue testing,” Risinger adds, “the next batch is manufactured using the exact same alloy and process.”
Based in New Hudson, MI, PSI provides custom valve springs to professional engine builders whose clients compete at some of the highest levels of motorsports, including NASCAR, IndyCar, NHRA, Rally, and Supercross. The catalog also features part numbers for Sprint Cars, Late Models, Sportsman drag racing, performance street cars, and other segments. Additionally, PSI produces springs for emerging applications like the Coyote and Godzilla engine platforms.
Because most of PSI’s customers are developing highly specialized, one-off engines, Jeff Villemure explains that they don’t typically share the hardware that’s required to conduct Spintron or dyno testing. Likewise, customers prefer to perform their own dynamic simulations and validation testing.
Even though certain steps in the process are kept close to the vest, Villemure was able to provide an overview on how springs progress from concept through development. He notes that customers often approach PSI with a need for enhanced performance, whether they want to achieve that by adding valve lift or more rpm.
“We can work with them to design a spring that will provide the increased loads and/or clearance to coil bind to support those engine changes,” Villemure says. “Of course, these spring changes must fit within the packaging constraints of their engine and last the expected lifetime of the engine service. This requires a deep understanding of the complex interplay between spring specifications, engine geometry and long-term durability.”
Under another scenario, an engine builder may be looking to reduce mass from the valvetrain. The objective, then, is to design a spring that’s smaller, lighter, and higher frequency, yet still delivers the forces capable of controlling the valvetrain. While cutting mass out of the equation can enhance the engine’s overall responsiveness and power delivery, it does require a high degree of sophistication in product engineering.
“We’ll use our software that was developed in-house to help us design those new springs,” Villemure explains, adding that historical data and years of experience help determine aspects like stress limits and the precise manufacturing process that will be followed for each application type. This proprietary software and specialized knowledge allow PSI to speed up development of its spring designs and help predict how they’ll respond in real-world applications.
Subsequent testing verifies and validates those processes. PSI checks each spring for coil bind height, and sorts them into load groups to save the engine builders assembly time.
“We also have the capability to check the polished surface roughness using a profilometer, the residual stress by means of X-Ray Diffraction, and micro hardness to verify that our heat treatment and nitriding process was applied correctly,” Villemure says.
These protocols ensure that every spring meets PSI’s standards for dimensional accuracy, surface finish and material properties.
“In addition to these checks,” he adds, “we also offer various levels of visual inspections to find any major surface defects that might be left over after polishing, and sorting by loads or coil bind into tighter groupings.”
No matter the manufacturer, a lot goes into testing and ensuring valve springs will hold up to the ever-greater stresses of today’s engine valvetrains. EB
Engine builders looking to move the needle on a certain engine platform might decide to design and develop their own billet block.
The utilization of billet blocks in high-performance engine building is no longer reserved for the select few. Collectively, the industry has reached the necessary heights across various applications where a billet block is the way to go, and as such, many billet block options now exist. Not only does a billet block offer builders and racers the ability to handle more horsepower and make easier repairs (in many cases), but it also offers the ability to change aspects of the existing block for the better.
Manufacturers are utilizing new technology and engineering techniques to continually make rocker arm systems better, and more specific to certain applications.
Valve manufacturers are constantly refining valve design and performance to provide solutions builders need.
Lifters play a crucial role in an engine’s valvetrain, so understand what to look for to keep your engines running without issues.
In today’s camshaft design and selection process, you have to see your engine as a system and often end with the camshaft, not start with it.
Engine Builder and Engine Pro present Shop Solutions to provide machine shop owners and engine builders the opportunity to share their knowledge to benefit the entire industry.
The GT40 Drop-In Valve Spring Kit comes with 1.486″ single valve springs, valve spring retainers, metal body Viton valve stem seals, and eight standard and eight +.050″ valve locks.
Dura-Bond has decided to expand its focus from only engine to include powertrain. The company sees powertrain as the new future of this industry.
Those who submit Shop Solutions that are published are awarded a prepaid $100 Visa gift card from Engine Pro.
duo check valve Content for engine professionals and enthusiasts