part 3
What about if you’re building an engine based around a power-adder? If you’re going to spray some nitrous you won’t have to use anything exotic when it comes to valvesprings and valvespring pressure. You just need to make sure the valve spring pressure addresses the engine’s RPM and application needs. Now, if you plan on pushing a lot of boost into your engine, things get a little more complicated when it comes to valve spring pressures.
“In a boosted application with very high boost numbers, you should take into consideration that the backside of the inlet valve is under constant static pressure, which does indeed diminish the seat pressure. The question is, how much does it diminish and do I really need to seriously consider it in my valve spring choice? Let’s say you have a typical valve diameter of 2-inches, which works out to three-square inches of area on the backside. If you have a spring that has 300-pounds of seat pressure, a good rule of thumb is to deduct 10-pounds per square inch, which equates to 30-pounds maximum load at RPM. This brings the seat pressure down to 270 pounds,” Jamora explains.
ISKY puts their valve springs through many different tests to ensure they will work as designed.
So, when it comes down to it, how do you pick the correct valvespring that has the right pressure for your application? There are a few parts that go into this process, including talking with camshaft manufactures so you can talk about your camshaft selection and how it will interact with all the valvetrain parts you want to use. Jamora also has some words of wisdom to help you select the right valvesprings.
“The goal is efficiency, not effectiveness. What I mean by that is you can always throw a ton of spring pressure at a combo that has been having spring problems and the solution can be effective, but having needless extra spring pressure does cost horsepower. It’s better to understand the dynamics of a combo and chose a spring around that. While we need heavy pressures on the open side to keep the lifter on the cam and return the valve to the seat, the real stress to the valvetrain is the offset load flex during the wind up of the cam.”
Jamora also adds, “The load on the parts is at its highest off the seat as the valve opens and sends a shockwave to the pushrods and the rest of the valvetrain. If you can reduce seat pressure while keeping the system in a controlled state as well as keeping the frictional losses at a minimum then you are at your most efficient.”
As you can see, selecting the right valve springs with the correct amount of pressure takes a bit of research. By taking the time to get a set of springs that is matched to the rest of your valvetrain and your application, the possibility of valve spring failure is greatly reduced.
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ISKY Racing Cams
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