Erson Cams Explains The Fine Points Of Racing Valve Springs

Valve springs are one of the most complex subjects surrounding racing engine components. Most engine parts individually function in a set spinning, rocking, or straight line motion. The operation of the valve spring has complexities like pressure, compression, and rebound functions, which cycles your valvetrain as the cam lift wishes. PBM/Erson Cams helps us simplify three major points in valve spring applications.

Coil Bind

Related to maximum valve lift, when a valve is fully opened—most engine builders set up the valve spring to be just short of coil bind, which returns the spring to a uniform, stable shape on every closing cycle. When the spring reaches maximum compression, only a few coils in the middle have a small gap, within .050- to .060-inch.

This borderline coil bind prevents excessive space between the coils, allowing a relaxed state. If you look at a high-speed video of a spring in operation, it constantly shakes and wiggles. Specifying and assembling your heads with the springs at a minimum compressed height lessens these excess spring bounce motions.

Lance Stillwell is one of PBM/Erson Cams engineers preparing for another dyno session to develop new FSP Professional valve spring designs.

Valve Spring Clearances

Another critical measurement is at the valve spring’s corner radius at both surface ends. Clearance between the spring’s coil diameter is vital as it fits onto the valve keeper and the cylinder head machined pocket.

The mating corners must be at a lesser radius than the spring diameter to prevent binding or a spring resting unevenly. Also, excessive clearance between the spring and pocket provokes unwanted “walking” of the spring. This clearance can be corrected by installing spring cups between the head and spring.

Seat Pressures

The choice of single, double, and triple springs is based upon the amount of pressure necessary for the lifter to remain on the cam lobe.

As engine speed increases, so does the inertia of the numerous valvetrain components. The spring must overcome this inertial force of the overall valvetrain to make an immediate and opposite motion when the cam travels past peak lift.

The spring pocket and the valve keeper must clear the spring wire diameter as not to cause a binding or uneven seat of the valve spring. The assembly process is as much about checking clearances as putting together your engine.

Too much valve spring pressure costs horsepower when unnecessary engine force is required to open your valve springs. Using the lightest spring to control the valve is best, but cylinder pressure is lost with too weak of a spring pressure.

Valve chatter means the valve continues to bounce on the seat when it is not closed by necessary spring pressure. The ultimate version of this similar problem is called “valve float,” where the valvetrain is out of control, and the lifters have lost contact with the cam lobes.

Pressures Not Too High, Not Too Low

Erson’s FSP series of valve springs are available for drag racing and many other motorsport applications. The use of high-quality materials is paramount to creating successful competition valve springs.

The key to accurate springs comes from ultra-strong, specifically blended, pure steel alloy wire. Spring pressures not overly high or low will create a racing engine with long life and result in the most horsepower. Prevent a “party” of motion that results in damage anywhere related to the valvetrain.

Article Sources

About the author

Todd Silvey

Todd has been a hardcore drag racing journalist since 1987. He is constantly on both sides of the guardwall from racing photography and editorship to drag racing cars of every shape and class.
Read My Articles
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