An aftermarket exhaust manifold designed to optimize exhaust flow from the cylinder head to the rest of the exhaust system. Increases power.
Header (also called exhaust manifold or manifold) is an aftermarket replacement for the stock exhaust manifold. Headers route exhaust gas from the cylinder head to the rest of the exhaust system. Aftermarket headers are designed for optimal flow, often using equal-length tubing and stepped diameters to maximize exhaust velocity and reduce backpressure on the engine.
Headers are particularly important for naturally aspirated engines and at higher RPM where exhaust flow demands are highest. The benefit of a header upgrade is typically 10-25 horsepower on naturally aspirated cars, less on turbocharged cars (where the turbo housing dominates exhaust flow). Quality matters significantly: a poorly designed header can hurt rather than help power output.
Common header types include shorty headers (short equal-length tubes that fit close to the engine), tri-Y headers (three-into-one design with intermediate junctions), and long-tube headers (full-length equal-length tubes that extend further before merging). Each has different power characteristics and packaging requirements. Long-tube headers typically produce the best high-RPM power but require more installation work.