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Valve Tech Questions


Manufacturers of race engine valves address some of their most common technical questions.

By John F. Katz

Lately we’ve found it enlightening to ask the manufacturers we interview about the tech questions they receive. In this case, what do racers want to know about the valves they are considering buying—or perhaps have just bought?

Ian A. Levitt of QualCast in Nashville, Tennessee, reported that “the most common questions generally concern installed heights, the hardness of the guides, or seat materials for specific applications.”

Ken Sink of Milodon in Simi Valley, California, confirmed that most questions concern dimensions: “What stem diameters do we offer? What head diameters are available? What valve lengths are available—and how much do they weigh?”

Engine Pro in Wheat Ridge, Colorado, said Don Weber, most commonly fields inquiries about its Nitro Black process. “Often, people think that nitriding is a coating. It is not. It does not change the dimensions of the valve. It does change the metallurgy, increasing both the hardness and the ductility of the entire valve.

“People also ask where our valves are made,” Weber continued. “Our factory in Argentina is both an OE and performance valve supplier, and has been making valves for 50 years. And, of course, all Engine Pro valves are made to our specification.”

“Many times customers ask about weight versus durability,” added Melissa Blackwell-White of CV Products’ Xceldyne division, Thomasville, North Carolina. “The answer depends on the customer’s budget, and the number of races scheduled before a rebuild. Ultimate performance has a direct impact on component life. Another frequently asked question is, ‘What do coatings do, and are they worth the money?’ The answer is simple: In most cases coatings will save money by prolonging component life.”

Blackwell-White also cited an unusual question: “Do I really need racing valves?” The answer: “Are you racing?”

“Two of the most common questions we get are related to valve weight and required spring force,” said Will Kibblewhite of Kibblewhite Precision Machining, Pacifica, California. “The two questions are really opposite sides of the same coin. Some customers who are looking for every last bit of acceleration and the absolute minimum amount of parasitic loss, and want to know how much they can reduce their valve spring force if they convert from steel to titanium valves. Of course, the question is a bit more complex than it seems. The best way to determine the answer is to run a computer simulation of the current system, and then run a second simulation with the reduced valve mass. And then, you also have to determine if the customer is going to maintain the current maximum, or if they plan to try to take advantage of the reduced mass by increasing rpm. Only once we have all of the operating parameters can a determination be made on required spring force.

“On the flip side,” he continued, “some customers want to know if they can increase valve durability/longevity by converting from titanium valves to steel, and what type of spring force increase will be required to make the conversion. Again, the best way to determine that is to look at the entire system, and run a simulation. In some cases, a seat material change may help address the issue. A softer material may increase the life of the titanium valve face. Or, we may discover that given the cam profile and the rpm, the current spring force isn’t enough to control the titanium valve, and more spring force would help address the issue. Or, we may find that the cam generates a harmonic that causes the valve spring problems, and another spring with similar force but a different natural frequency may solve the problem.

“Ultimately the customer may decide to switch to steel valves because once the system is set up correctly, replacement intervals may be longer, and cost for the steel valves is probably going to be quite a bit less than titanium valves.

“The key is being able to examine all of the variables so that the customer can make an informed decision,” concluded Kibblewhite.

Valve Tech Questions

Numerous calls come across valve manufacturers’ tech lines daily. Beyond specific questions regarding installed heights, hardness of the guides, stem diameters, and many others, one supplier responded to the common question, “Do I really need racing valves?” The answer, she replied: “Are you racing?”


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