Special section--camshafts and valvetrains: High-performance valves

National Dragster, Mar 7, 2003 by Jodauga, John

New manufacturing breakthroughs have advanced the technology and science of racing-valve designs

Though high-performance valves have been available practically since the first internalcombustion engine was introduced, significant gains in materials and manufacturing methodology continue to increase performance.

Manley Performance General Manager Michael Tokarchik said, "We've seen major development with some nickel-based alloys that are primarily developed within the European aircraft industry. These alloys, which have proven to be very durable in jet-turbine-engine applications, have become popular for Top Fuel exhaust valves, which encounter exhaust-gas temperatures of almost 2,000 degrees [Fahrenheit]. These alloys have been employed in our new XH432 Xtremealloy exhaust valves, which are made for such applications."

Racing Engine Valves' (REV) technical director of product development, Ralph Lebron, said, "Our newest breakthrough is our Nimonic 90, which is used for extreme heat and high cylinder pressures. It is normally found in nitromethane powerplants and high-boost turbo applications, such as multiple-turbo tractor-pull engines. This material will endure temperatures well into the 2,000-- degree range without distortion."

Tokarchik added, "What has recently changed the most is the heat-treating process. It wasn't that long ago when valves got a simple one-stage heat treatment. Now, we have multiple heat-treatment procedures that feature two or three stages and result in improved grain refinement and enhanced properties, which make the material almost like a new alloy in its operational behavior."

The continued advancement in CNC technology has also raised the bar in valve-manufacturing standards.

"The most critical valve tolerances are now about one half of what they used to be, a feat that was not possible five or 20 years ago," said Tokarchik. "The new CNC technology, with improvements in turning and grinding and advances in chrome-plating techniques, has changed all of that."

As valve science has expanded through the years, so has the sophistication of racers, especially in the Sportsman ranks.

"More Sportsman racers, especially in the Super classes, are switching to titanium valves," said Tokarchik. "This may seem to be a bit of overkill at first, especially for classes running on a fixed index, but investing in titanium valves pays off in terms of less wear and tear on rocker arms and improved valve-spring life. They also allow for higher engine speeds and more aggressive camshaft profiles, a desirable asset for Super Gas and Super Comp racers who are looking for higher top-end speeds."

Regardless of the materials or manufacturing methods employed, the basic rules for choosing and using high-- performance valves remain in force.

Selecting valves for a particular application

CV Products/Del West Vice President of Sales Keith Bryant recommends that racers closely examine their intended racing environment before making a final choice.

"Durability for specific applications, maintenance intervals, and proper machining of complementary components, such as lightweight retainers, locks, and proper seats, enhance the titanium-valve package," said Bryant "In certain high-- temperature exhaust environments, such as nitro, blown, turbo, and some street vehicles, titanium valves are not the best choice. Titanium valves become more important as engine speed increases."

Lebron suggests that a racer take into account design and material options.

"First, look at the back angle and radius of the valve design," said Lebron. "REV is constantly testing new angles and radii to achieve optimum airflow in many of today's popular cylinder heads. Second, we choose a material based on the environment in which the valves will perform. Generally speaking, normally aspirated applications use a good quality EV-8 stainless material, but forced-induction engines need a higher-temperature material for hotter exhaust-gas temperatures. In those cases, we use our X-751 or Nimonic materials, 'which have higher nickel contents."

Tokarchik stressed valve longevity as an insurance factor.

"As with connecting rods, think of valves as a long-term investment in the reliability of an engine," said Tokarchik. "Buying cheap valves can lead to serious consequences. For instance, hard chrome costs more to apply and grind but holds up much better than flash chrome, which can flake or peel and cause valves to stick in the guide. The same basic stainless-steel alloy can be heat-treated in a number of different ways. Expensive and time-consuming methods produce the best results. Think of quality valves as insurance for your engine."

Chet Herbert, founder of Chet Herbert Cams, recommends that racers "use the biggest valve possible."

Future innovations

Valve manufacturers have several major breakthroughs on the immediate and upcoming horizons.

"Manley has introduced its Gen II program, which makes it easy for professional engine builders and race teams to obtain custom-made valves," said Tokarchik. "Essentially, Manley makes large runs of popular' stem sizes, then can tailor the length, groove position, head diameter, margin, and other specs to order. We plan to expand the Gen II program in terms of base, valve-blank availabilities, and modification range in the near future."