Beehive BuzzComp Cams now offers new valvesprings that take advantage of this conical-shape technology to complement our favorite engine. One of the engines we have always had difficulty controlling is a big-block Chevy outfitted with a set of hydraulic-roller lifters. This is due in large part to the weight of a typical big-block valvetrain, which uses large, heavy, 31/48-inch-diameter valve stems. We've experienced mild valve float as low as 5,500 rpm on a hydraulic-roller-cammed 454 H.O. engine.
To prove this point, we bolted up a GM Performance Parts 454 H.O. big-block to Ken Duttweiler's dyno and outfitted it with a Comp Cams Xtreme Energy 282 hydraulic-roller cam, along with a set of World Products Merlin Jenkins oval-port iron heads equipped with a set of Comp single-wire valvesprings (PN 911), which are the standard springs recommended for this cam. We outfitted the rest of the engine with an Edelbrock Performer RPM Air Gap intake, a 750-cfm Holley mechanical-secondary carb, and an MSD distributor sparked by a 6AL box.
Dyno man Ed Taylor performed the dyno test, equipping the Rat motor with the Comp 911 springs. At around 5,500 rpm, the engine went into serious valve float and would not rev past this point. Given the cam's duration and lift, it should have made power at least up to 5,700 rpm, but clearly the engine was limited by valve-control difficulties.
Comp then sent us a set of brand-new PN 29120 beehive springs designed specifically to address this valve-control problem on the Rat motor. As you can see by the accompanying spring-pressure chart, the beehive spring offers 30 pounds more load on the seat (part of this load is due to the shorter installed height), with open pressures within roughly 5 to 10 pounds. We installed these springs directly on the big-block heads with no prep work and with no other changes so we could do a direct comparative test.
Once the engine was back up to temperature, the first test with the new beehive Comp springs was a bit of a shock. We expected to see a slight increase in power above 5,000 rpm, but what we saw instead was a power increase virtually across the entire rpm band from 2,200 rpm to 5,700 rpm. There was only one point at 4,300 rpm where the power numbers were the same. Amazingly, we picked up 26 lb-ft at 2,400 rpm and then 20 hp at the top end at 5,600 rpm. The large gains also both occurred at the opposite ends of the rpm scale, with minimal changes in the middle.
We discussed this test with Comp Cam's spring design engineer Thomas Griffin, and he attributed the increase at low speeds to the additional load pumping the lifter down slightly, which could shorten the cam's duration and boost torque. To test that theory, we installed a set of Comp Cams mechanical-roller lifters and different pushrods to eliminate the hydraulic lifter as a variable. This is not a recommended procedure, but with a very tight 0.004-inch lash for a quick test, Comp felt we could get away with it. This test revealed 11 lb-ft less torque at 2,400 rpm than with the beehive springs and hydraulic lifters. This was at the 432 lb-ft that was the same exact rpm where we had gained as much as 26 lb-ft. This tells us that Griffin's theory was worth at least 11 lb-ft of the total 26 lb-ft change. However, this still leaves at least 15 lb-ft not accounted for.