HOLLEY SINGLE PLANE
The Holley was the first of the single-plane intakes to be tested. Like those that would follow, the Holley version demonstrated the inherent nature of the design by offering sizable gains in peak power production. In fact, the single-plane Holley offered improvements in peak power and torque compared to the dual-plane intakes, with peaks of 636 hp at 6,900 rpm and 557 lb-ft of torque at 5,000 rpm. Note that the peak power came higher in the rev range, but the peak torque actually occurred earlier than the dual plane. Despite offering more peak power and torque, torque production suffered down low with the single plane, as the 415 produced 499 lb-ft of torque at 4,000 rpm.