Which header prevents reversion with multiple diameters on each primary tube?

• A. Stepped Header
• B. Stock Header
• C. Dyno Header
• D. Custom Header

Answer: (A)

Stepped primaries use two different diameters within each tube to tune exhaust flow and pressure waves. That step keeps the gas velocity high in the early part of the pulse, which helps prevent backflow into the cylinder during valve overlap and reduces reversion. As the pulse moves into the larger-diameter section, the reduced restriction lets the flow continue smoothly, avoiding excessive reflections that would push exhaust back toward the valve. This combination of two diameters on every primary tube tunes the timing and energy of the pulses across a broad RPM range, improving scavenging and keeping exhaust moving forward. Stock headers with uniform primaries don’t provide that built-in velocity-timing benefit, and while a custom header could be designed with steps, the stepped approach is specifically aimed at preventing reversion with multiple diameters in each primary.