Intake and exhaust valves are exposed to every bit of heat and pressure that are generated during the combustion process — that’s a hard life, so they need to be battle-ready. The material used to make a valve is just part of how it can deal with the hot environment it lives in — the other is the finish applied to them. Engine Parts Pro uses a slick liquid nitriding process on its Nitro Black valves that make them ultra durable.
Valves are available in a variety of materials, from exotics like titanium to a more affordable material like stainless steel. The material dictates the price, and going with a full titanium valve can be overkill on a build. The 21-4N stainless steel valves with a nitride finish from Engine Pro are a perfect compromise for those who need a lot of durability and are on a budget.
Roger Borer from Engine Pro explains why the nitride finish on Nitro Black valves is so important to ensuring the valves can deal with high temperatures and chamber pressure.
“Because 75-percent of heat transfers through the head, seat width is critical. While a narrow seat can improve flow, heat will not transfer out of the valve as fast. Nitro Black’s hard nitride layer provides wear resistance, and the diffusion region underneath the nitride layer improves fatigue life. Both of these improve strength and heat resistance, which can help when choosing the narrower side of seat width specification. Because Nitro Black valves have a harder surface finish, they pair well with harder seat materials that are required for narrower seat width.”
Each batch of valves goes through a five-step process where they are first heated to 700 degrees Fahrenheit and then immersed in a solution that’s high in nitrogen and aerated. While the valves are in the solution, the temperature is raised to 1,100 degrees Fahrenheit. This step creates the hard nitride layer that’s diffused into the valve’s material permanently.
“After the first two steps, the valves then go into a 750-degree oxidizing salt bath. Reaction with the porous zone of iron nitride produces a black iron oxide layer, called magnetite, which improves corrosion resistance and dimensional stability. Valves are then cooled, rinsed, and polished. Post oxidizing immersion is the final step, creating a smooth, hard surface that can benefit airflow. This last step also furthers enhances corrosion resistance, a long term benefit to your build, and airflow,” Borer explains.
To learn more about Engine Pro’s Nitro Black valves head over to the company’s website right here.