Hooker 2-Inch Super Competition
The tti step header is different compared to all of the other headers tested. The tube diameter "steps", or increases in size, at about 5.5 inches from the header flange. The increase in diameter down the pipe allows for gas expansion, and provides a benefit in reducing reversion tendencies as compared to a straight pipe of a larger diameter pipe, especially in the critical area of the exhaust port exit. The upshot is the ability to run a large pipe diameter while minimizing the potential for a decrease in torque lower in the rpm range, thus providing a broader torque range.
Step headers have become popular in all-out drag racing classes, and they are proven to work. Theories abound about the mechanics of why this is true, including the notion that the step presents a cross-sectional area change, sufficient to reflect a low-pressure wave to improving the scavenging effect. Considering the tuned length of the short section of pipe to the first step, this seems unlikely. However, one thing that we have found conclusively, is that a larger pipe diameter can be employed while minimizing the torque penalty lower in the operating range.
The tti step header, at 2 1/8 inches for the majority of the primary pipe length is, by most formulas, on the large side for an engine at the performance level of our test 440. Had we been testing straight 2 1/8-inch headers, we would fully expect to see a drop in torque production below-peak-torque rpm, and very little, if any, gain higher up as compared to a 2-inch tube. With the stepped design, we actually posted a slightly-higher average torque number than with the 2-inch headers, and the highest peak horsepower of any of the headers tested. The edge was slight, but the numbers were up in every category, though the power curves followed those of the 2-inch header very closely. It is worth noting that the tti stepped headers we tried were nickel-chrome-plated steel. All of the other headers in our test were metallic ceramic coated, a coating which is claimed to provide a power enhancement, although we have never verified this directly or compared to chrome headers.
This tti seems to be well suited for high-output applications, and we have used them in big-block Mopars to well over 750 hp. The step makes them a flexible design, allowing the tti "steps" to be used successfully on engines with considerably less horsepower than this, while providing enough header capacity for the combination to grow as the engine is enhanced. With an engine combination like our 630hp test mule, we could use the bigger header now, and still be satisfied the header will be adequate if we moved up to serious race heads and moved the peak power upwards of 100 hp.
|The Pipe||tti 2-2 1/8 inch Step Header|
|Typical application||High output street/Race|
|Primary diameter||2 inch, stepping up to 2 1/8 at 5.5-inches from flange|
|Collector diameter||3 1/2 inch|
|Primary length||unequal length|
|Peak hp||636 hp @ 6,400 rpm|
|Peak torque||567.7 lb-ft @ 4,800 rpm|
|Average hp 3,000-6,600 rpm||490 hp|
|Average torque 3,000-6,600 rpm||532.7 lb-ft|
|Average torque 3,000-5,000 rpm||523.4 lb-ft|
|Average torque 5,000-6,600 rpm||548.8 lb-ft|