For several years, GM has employed a beehive-shaped spring in the LS1 engine. This spring's ovate or oval wire provides more lift without increasing the spring height. It also has a variable rate, meaning that when first compressed, the spring operates with a lower spring rate and progressively becomes stiffer as the smaller-diameter windings compress into the larger coils. Most importantly, the beehive shape reduces the weight of the spring. This is a critical point, because coil springs must use a certain amount of their pressure to control themselves. So, if we reduce the mass of the spring, more of the spring pressure should be available to maintain control of the valve, and it may be able to accommodate a higher engine speed. The beehive shape also uses a radically smaller and lighter retainer. This is important because we're reducing the mass at the top of the spring, which reduces lateral leverage as well. Keep in mind that the top of the spring travels much greater distances and is subjected to greater accelerative forces than the bottom of the spring.
Valve FloatBefore we go any further, it's important to define what we mean by loss of valve control. This is most often referred to as valve float because the common misconception is that the lifter launches itself off the nose of the cam. While this can and does occur, the more common result of a loss of valve control is when the valve bounces as it approaches the seat. Generally, this will happen to the intake valve first because of its greater weight. This results in a loss of engine power because cylinder pressure is pushed back into the intake manifold instead of remaining in the cylinder. The biggest problem is identifying when the power loss occurs, because it may happen a few hundred rpm earlier than what is considered normal for a given application.
Classic valve float is usually accompanied by a dramatic loss in power and an obvious misfire, but most engines are already suffering power loss from valve float before it becomes audibly noticeable. This is what happened to our big-block and why our engine picked up significant power at the top end of the curve.
Don't Freq OutMost springs are rated for a certain load at a given installed height. That load is the pressure imparted on the valve to control it. Historically, load has been the main factor in matching a spring to a valvetrain, but given all the variables of rocker ratios, valvetrain weight, pushrod deflection, and a couple of dozen other items that affect valve operation, it's easy to see that matching a spring to a cam lobe and valvetrain requires much more data than just a load rating. Much of this has to do with what is called a spring's natural frequency.
At a given rpm, any valvespring will hit a frequency where it will naturally vibrate or resonate like a tuning fork. When this happens, the spring loses much of its ability to maintain control over the valve. This is why most single-wire valvesprings come with a flat wire damper. This damper is designed specifically to dampen the spring's natural frequency, especially when the spring resonates at an rpm where the engine spends time. Dual or triple springs use the friction between the inner and outer springs to perform this damping action.
The beauty of the beehive spring is that its conical shape and variable rate creates numerous, yet less dramatic, natural frequencies, which makes it much less susceptible to a loss of control. There's much more to this concept that would take volumes to discuss (and frankly we don't pretend to understand all of it anyway), but it's enough to say that the beehive spring takes advantage of the physics of its design to give it much more control.