Which header arrangement is designed to prevent reversion by using multiple diameters on each primary tube?

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

Answer: (D)

When exhaust gas flow tries to reverse back into the cylinder, it’s driven by pressure waves from the firing event. The way a header shapes those waves can reduce or promote reversion. A stepped header uses multiple diameters along each primary tube to create intentional impedance changes that tune how pressure waves reflect and travel.

The smaller-diameter portion speeds the gas and raises its momentum right as it exits the cylinder, which helps pull in the next portion of exhaust and improves scavenging. As the pulse travels farther, the pipe expands to a larger diameter, which reduces velocity and smooths the expanding wave. This combination of a velocity boost followed by a controlled expansion reshapes the pressure waves so that reflections are less likely to push exhaust back into the cylinder. In effect, the stepped design better aligns the exhaust pulses with the engine’s firing order and RPM range, minimizing reversion and improving scavenging.

Other header types don’t intentionally employ this two-diameter impedance strategy, so they’re less focused on preventing backflow through wave timing.