"The nature of a beehive spring is that it has a progressive rate," Godbold explained. "Each coil has its own resonance frequency. It's not just magic-there's a reason it works. It's hard to make the whole thing resonate." Remember, however, that resonance is also a function of a spring's weight, as well as its spring rate. Higher spring rate usually leads to a physically heavier spring, but using a beehive spring allowed us to maintain the same spring rate while cutting valvespring and retainer weight in half.
"All we did was move the limit speed up, and the limit speed was close to peak power," Godbold summed up. When compared to the "gorilla method," which would have mandated a bigger, heavier spring, this is a finesse approach. We are actually able to obtain better control with less seat load, open load, and spring rate by substantially reducing the mass, thereby increasing the natural frequency. Our post-peak dip is gone, and the thing revs to seven grand without a complaint. Sure, power still drops off after the peak, but not as abruptly-up high, our rev-happy 406 is now making 40-some horsepower more than it did. We'll take it.
Before submitting our Coast High Performance-built 406 stroker to a round of high-rpm dyno testing, we installed a set of Comp Cams Pro Magnum hydraulic-roller lifters. They don't look any different from the regular High Energy lifters, but they're internally designed to perform at higher engine speeds. "The Pro Magnum lifter has less oil volume," Comp's Billy Godbold explained. "The valving and geometry are set up to handle high rpm." These lifters also have a low bleed-down rate and less plunger travel, which means they require a bit more attention when it comes to setting preload. They aren't, however, a cure-all. "They'll solve a lifter issue, not a valve issue," said Godbold. "The lifter was fine; the valve was bouncing." Indeed, Comp's regular-issue handled our 6,500-rpm abuse just fine. Looking to the long run, however, we went for the upgrade. Godbold endorsed our choice: "It's set up to be a very stout lifter. It's really good insurance."
While our two sets of springs...
While our two sets of springs sported similar rates, they're radically different in size and weight. Put simply, a smaller, lighter spring is easier to control. Comp's Godbold elaborated: "The coil moves faster than anything else, and the top of the coil moves faster yet-it actually outruns the retainer." Beehive springs are narrower-and therefore lighter-at the top for this very reason.
For this round of testing,...
For this round of testing, Westech's Steve Brul outfitted our 406 with an air hat. This deceptively simple apparatus measures the flow of air into the engine. Since loss of valve control disrupts this airflow,...
...the air hat measures that...
...the air hat measures that as well. The evidence of this disruption was graphically demonstrated.
To a certain extent, installing a stiffer valvespring improves valve control and reduces issues like valve bounce. On the other hand, stiffer valvesprings tend to be heavier, and weight is the enemy when it comes to high-performance valvetrains. Heavier springs are harder to control, and are harder on the rest of the valvetrain. Installing beehive valvesprings allowed us to have our cake and eat it too. Our springs had nearly identical seat and open-load figures, but the newfangled beehives weigh nearly half as much, and stayed in control where the traditional coils strayed.
| ||OLD ||BEEHIVE ||DIFFERENCE |
|SPRING ||114.2g ||69.5g ||-44.7g |
|RETAINER ||15.7g ||6.0g ||-9.7g |
|TOTAL ||-54.4g |