July '16

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JULY 2016 THE SHOP 65 PERFORMANCE W hile a standard exhaust manifold collects and routes all exhaust ports to a single outlet in close proximity to the cylinder head, automotive exhaust headers provide a dedicated tube for each cylinder head exhaust port. Individual header pipes are referred to as primary pipes or primary tubes. On header designs that feature the bank of primary tubes that terminate into a common outlet, this common outlet is referred to as the collector (where all of the cylinder head's primary tubes are "collected" together as a group). An exhaust header, since it provides an individual primary tube for each cylinder, provides a more efficient and more evenly balanced exhaust path for each cylinder, with far less backpressure. Conventional wisdom dictates that the exhaust header tubes for each cylinder head will feature equal lengths, allowing each cylinder's exhaust flow and pressure to be somewhat equal in nature. In reality, depending on the specific engine and vehicle, equal-length headers m a y o r m a y n o t b e p r a c t i c a l , simply in terms of fit and available space. In certain race applications, engine tuners sometimes experiment with different-length primary tubes in order to take advantage of camshaft profile and timing. For the street, we tend to favor equal- length tubes where space allows. Regard- less, the use of headers (as opposed to exhaust manifolds) should, in most cases, provide a performance benefit and allow the engine to breathe more freely with less restriction. In addition, a tubular header provides a weight reduction as compared to most cast iron exhaust manifolds. HEADER STYLES Commonly available header styles include shorty (often called block-hugger), full- length (often called long tube), Lakester or lake- style, and Tri-Y styles. Long-tube headers are usually designed with (in the case of an 8-cyl- inder engine) four primary tubes that merge into a single collector. Long-tube headers generally A look at styles, materials, performance & more. By Mike Mavrigian Getting Ahead on Getting Ahead on Getting Ahead on HEADERS An array of stainless steel exhaust headers with flanges welded, ready for collector installation. Shorty head- Shorty head- ers are often a ers are often a good choice for good choice for "universal" ve- "universal" ve- hicle applications. hicle applications. While equal-length primaries help to promote engine efficiency, for the street it's not a real concern.

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