Most dual-valvespring packages...
Most dual-valvespring packages include an inner and outer spring, as well as an internal damper. The damper is sandwiched between the two and uses the friction it creates to minimize spring surge.
HPP: In what applications are (traditional-shaped) single-springs best suited?
TG: Generally speaking, a single cylindrical spring package is sufficient for low-rpm applications with mild camshafts and low valve lift. Modern single-coil beehive springs are a different story, however. They're designed for today's engines, which typically feature more valve lift and operate at higher speeds.
HPP: At what point do dual- or triple-springs become necessary?
TG: There are just too many variables to suggest a specific point when either spring package becomes necessary, but traditionally speaking, dual-cylindrical springs are required when using a camshaft with a high valve-acceleration rate or when running a heavy valvetrain at high engine speed. Triple-springs are used in applications where dual-springs can't sufficiently control the valve through the entire event.
A point to remember when dealing with valvesprings is that there are measurable losses associated with having "too much" spring. Overall spring weight, coupled with the resistance forces associated with dual- or triple-springs, results in higher inertial forces, and that can add load to the system. This load can cause valve-timing changes at low, mid, and high lift, and that can affect the overall curve of the valve event. The result is an airflow disruption that lessens horsepower and torque.
Conical-shaped springs start...
Conical-shaped springs start with a wide base and taper toward the top, while beehive springs, such as these from Comp Cams, are mostly cylindrical, tapering over the top two coils. The appearance and function of the two types is similar.
As dual-spring technology continues making great strides, we're able to use duals where triples were once necessary, and we're finding instances when a single beehive spring can be used in place of a dual-spring. If there's any question of which is best for a specific application, our technical-support staff and engine-build salesmen are prepared to assist customers with the proper selection.
HPP: You've mentioned "beehive" springs several times. I've also seen such springs referenced as "conical." Are there differences between the two, and can you explain the advantages over a cylindrical-shaped valvespring?
TG: A beehive spring is cylindrical for most of the body length and tapers over the top two coils. A conical spring tapers gradually over the entire length of the spring body. Both types drastically reduce the moving mass of the spring and allow the use of a smaller diameter retainer. That frees up the power losses associated with the friction generated from added valvetrain mass, increased spring loads, and component deflection.
In addition to improved valve...
In addition to improved valve control and their tuning effect, modern beehive-type springs allow the use of a much smaller valvespring retainer. The unit on the right is used with a typical cylindrical spring, while the smaller unit at left is used with a beehive-type. The reduction in valvetrain mass allows for better valve control at high engine speed.
HPP: In what applications are beehive/ conical springs popular?
TG: Most of today's production vehicles are factory-equipped with beehive-type valvesprings constructed with ovate wire. The materials and manufacturing techniques we use at Comp Cams to produce our line of performance beehive springs is at a race level. They're quite popular in late-model performance builds but have a growing popularity in vintage applications, too.
It seems that those hobbyists with hydraulic rollers and some aggressive hydraulic- and solid flat-tappet camshafts are seeing horsepower gains and can rev their engines higher when using a lighter-load beehive in place of a heavier dual-spring package, but it all depends on the application and engine speed involved.
HPP: What is the thought process between install height, wire diameter, number of coils, and overall shape when designing valvesprings?
TG: Valvesprings incorporate certain load ranges at certain installed and open heights, with a specific amount of clearance between open height and coil bind. A critical consideration when designing a valvespring is the amount of vertical space the unit has to work within (spring height) and the certain harmonic frequency it resonates at during normal operation. We then construct it of the smallest wire and body diameters that will handle the stresses involved, while providing the desired natural frequency. The number of coils is a byproduct of this.