An engine's valvesprings play a critical role in its performance, yet those incorrectly chosen for a given application can cause hobbyists to unknowingly point blame in another direction if an engine doesn't live up to its full potential. While it seems that many are familiar with valvespring basics, you may be surprised to learn that they are among the most highly stressed components of the entire engine assembly-and the most misunderstood.
Like all other facets of the hobby, valvespring technology is rapidly changing. Not only are the materials and manufacturing processes continually improving, but cylindrical multispring packages are being replaced by uniquely shaped single-spring units in myriad applications. Comp Cams in Memphis, Tennessee, is one company that's at the forefront of that technology, and we contacted Comp engineer Thomas Griffin for his insights. Here's what he shared with us.
The load placed on the valvespring...
The load placed on the valvespring increases the higher an engine operates. When designing or selecting them for a given combination, valvetrain engineers must consider all of the components being employed. Overall valvetrain weight includes the valve, valvespring, retainer, and lock, and can oftentimes dictate an engine's maximum speed.
High Performance Pontiac: What is your present position with Comp Cams, and how long have you been with the company?
Thomas Griffin: I've been with Comp Cams for 16 years and am now a senior project engineer. I began my career building the static and dynamic testing lab for valvetrain components, and I acquired a wealth of hands-on experience as a test engineer dealing with valvetrains. That includes those engines found in street cars, sportsman class racing, NHRA Pro-Series, and most types of NASCAR racing. I progressed into component and system design; my primary functions now are valvespring design and project management.
HPP: In simplest terms, what is the purpose of a valvespring?
TG: Its function is to control valve motion while the camshaft forces the valve open and to keep the valve closed between valve events, but it must also dampen the resonant harmonics it generates during that action.
HPP: What materials are used to produce valvesprings?
TG: The stresses that valvesprings endure continually escalate with the constant push to run faster, and that typically means increased engine speed and valve lift. The materials from which they're constructed are becoming increasingly stronger, and the processes are making the pieces last longer under harsher conditions.
The most widely used materials employed today are super-clean chrome silicon alloys. Chrome silicon (CS) is the base alloy, and several alloying elements are added to enhance properties such as fatigue life and tensile strength. Material scientists are constantly experimenting with different alloying agents in an attempt to improve upon them.
Traditional dual-valvesprings...
Traditional dual-valvesprings such as these were commonplace on vintage Pontiac engines. Remaining quite popular today, technology has brought us new advances that improve effectiveness and even allow the use of dual-spring packages where high-pressure, triple-spring packages were once required.
Other materials such as chrome vanadium (CV) were popular years ago, but the CS alloys have since replaced it. Vanadium itself, however, is still widely used as an alloying agent due to its desirable qualities. Titanium is another, but its use is limited to a few drag-race applications because of its metallurgy and unpredictability in long-term fatigue situations. H-11 tool steel is also used in drag-racing applications because of its high tensile strength, but it, too, has its limitations.
HPP: What shape is the wire that's used to produce valvesprings?
TG: There are two wire shapes commonly used today to construct valvesprings: Most wire is round, while some is ovate, or egg-shaped. Ovate wire is essentially round wire with material added along the inside diameter of the spring body where the highest stress is located. The added material reduces overall stress, thus adding life to the component.
A benefit of an ovate wire spring is that it can be used when a round wire unit cannot. Situations might include when trying to squeeze more lift into a smaller spring pocket or when stresses are too high for round wire in a given spring package. Simply stated, it allows for more material to occupy the same given vertical space. A drawback of ovate wire is its manufacturing expense. It's more difficult to produce, and the price reflects that.