March - April 2012 Motor State Performance Report Article By Jim Kaekel, Jr.
Innovation is key when increasing engine efficiency and adding horsepower. Top racers, engine builders and other performance enthusiasts have learned that keeping an open mind to new products or ideas and incorporating them into their program will prevent being "stuck in time." Many innovations in automotive racing can be traced back to their origins in aircraft technology (often military).
Nitrous oxide systems, for example, were used as performance boosters in military aircraft during World War II, long before their use in automobiles. Lightweight batteries, widely used in many modern race cars, were developed for use in military aircraft as well. Beehive valve springs were also first used in aircraft applications, and this brings us to our tech topic.
Although beehive valve springs had been used in aircraft since the early 1900's, it wasn't until their introduction during the late 1990's as standard equipment in GM LS, Ford Modular and Dodge Hemi V8 engines that many performance enthusiasts began to take notice. According to Jason Youds of PAC Racing Springs, NASCAR teams have embraced this venerable spring technology, using beehive springs on restrictor plate engines.
Beehive springs continue to gain popularity in both the circle track and drag racing markets, particularly for classes that have strict rules regarding valve spring sizing or that disallow lightweight titanium valve train components. As a result of their increasing popularity, aftermarket manufacturers, including PAC, are offering beehive springs for many applications, including earlier engines originally equipped with conventional valve springs.
While traditional valve springs have a constant diameter, a beehive spring tapers in toward the top, making it resemble a real beehive, hence the name. Beehive springs are formed from ovate (oval) wire instead of traditional round wire. The conical shape and ovate wire yield a lighter spring for improved performance, equal stress distribution and a progressive spring rate. A beehive spring can offer more lift without increasing spring height, according to Youds. Most importantly, the ovate wire resists harmonics, a characteristic that eventually leads to harmful valve float.
The beehive spring's smaller diameter top allows use of a smaller, specially designed retainer for further weight reduction. These retainers weigh roughly 50% less than a titanium retainer for a conventional valve spring. Engine builders know that reducing valve train weight, specifically on the valve side of the rocker arm, multiplies the lobe acceleration rate by the rocker ratio and results in increased RPM potential without loss of valve control. That is why titanium valve spring retainers, valve locks and valves have become standard equipment on many high end racing engines. Titanium valves and their related components have their place in motorsports, but are typically out of the realm of the sportsman racer or street enthusiast budget. A set of beehive springs and lightweight steel retainers can be purchased for less than $200.00.
Beehive springs have proven very reliable, but may not be for everyone. They are generally not designed for use with camshafts that require over 200 lbs. of valve spring seat pressure or have greater than .650" valve lift. Detractors point out that, in the rare occurrence that a spring breaks, no safety margin exists due to the single spring design and that valve-to-piston contact could ruin an engine. A double or triple spring could prevent this occurrence. When beehive springs are used, particularly in a racing application, the springs should be replaced if any significant spring pressure has been lost due to fatigue, according to Youds.
The development of beehive valve springs has been expedited through the use of the Spintron, a device that PAC Racing Springs and Comp Cams use to rapidly spin an engine, less the lower rotating assembly, while cameras, sensors and lasers are used to study what happens inside the engine. Valve train experts study this data and use it to either improve an existing product or create a new one.