When the 1 7/8-inch headers were compared to the larger tubes tested later, the overall average output was about the same. however, these headers clearly favored output below peak torque rpm, while the big pipes proved superior higher up. For general purpose, high-performance use in the 475-575hp range, the 1 7/8-inch header is the size to get.

The Pipestti 1 7/8 inch
Typical applicationDual purpose/Race
Primary diameter1 7/8 inch
Collector diameter3 inch
Primary lengthunequal length
Peak hp616 hp @ 6,500 rpm
Peak torque570.5 lb-ft @ 4,800 rpm
Average hp 3,000-6,600 rpm488 hp
Average torque 3,000-6,600 rpm533.1 lb-ft
Average torque 3,000-5,000 rpm532.2 lb-ft
Average torque 5,000-6,600 rpm536 lb-ft

Hooker 2-Inch Super Competition
Moving to the larger 2-inch Hooker Super Comps, the engine responded with a significant increase in top-end horsepower, upping the output by 18 hp. Looking at the averages, however, the gain came at a price. The averages over our entire test range were within 1 hp and 1lb-ft of the 1 7/8-inch header, indicating that as far as overall output over the engine's test range was concerned, it was almost a dead heat.

The difference between the 1 7/8 and 2-inch headers was simply where the power comes in. The torque averages above and below 5,000 rpm (approximately peak torque rpm) shows that the larger tubes added to output up top, while subtracting a similar amount down low. Essentially, the larger tubes tilted the torque curve around peak torque, with more up high, and less down low, for nearly identical averages. Interestingly, peak torque rpm moved up 500 rpm, a significant amount. The larger 3 1/2-inch collector diameter likely had a large part to play in that change.

The PipesHooker 2-inch Super Competion
Typical applicationDual purpose/Race
Primary diameter2 inch
Collector diameter3.5 inch
Primary length32 inch
Peak hp634 hp @ 6,400 rpm
Peak torque568.4 lb-ft @ 5,300 rpm
Average hp 3,000-6,600 rpm489 hp
Average torque 3,000-6,600 rpm531.4 lb-ft
Average torque 3,000-5,000 rpm521.7 lb-ft
Average torque 5,000-6,600 rpm545.4 lb-ft