Header (Exhaust Header)

The header, or header pipe, is the front part of the exhaust system. It bolts to the exhaust ports on the cylinder head and carries hot gases towards the collector, catalytic converter and silencer. On multi-cylinder engines the separate pipes merge in a collector, for example in 4-into-1 or 4-2-1 layouts.

Header length and diameter affect where in the rev range the engine makes its power. On two-strokes the equivalent part is the expansion chamber, whose shape is crucial for performance.

Headers get very hot and can discolour; this is normal on stainless steel. Check for blowing exhaust gaskets at the port, which cause a ticking noise and can upset fuelling readings from lambda sensors.