Engines have often been compared to air pumps, because the engine that's most efficient in terms of economy and power is the one that can get air in and out of its cylinders the easiest. That's why most performance modifications like conical air filters, cold air intake systems, headers, and cat-back exhaust systems are aimed at making the intake and exhaust systems less restrictive. These parts increase the flow of air into the engine and ease the flow of exhaust gas out of the engine. Among these components, headers may be the most difficult to install. In this article, we'll discuss what headers do, their different types, and how much performance they can add to your car.
Headers take the place of your exhaust manifolds, which are the first part of your exhaust system between the cylinder heads and the front exhaust pipes. They are constructed of individual tubes (one for each exhaust port) that meet in a larger tube called a collector. Headers are installed because they boost the rate of exhaust flow out of your engine compared to OEM stock exhaust manifolds, which are typically designed to take up as little space as possible. However, as we will see, the quality of manifold exhaust flow rate varies from vehicle to vehicle. Regardless of the manifold, we recommend making the rest of your exhaust system less restrictive before you install headers. This means installing larger-diameter, mandrel bent exhaust pipes, and it definitely means using freer-flowing mufflers. There's no benefit to putting headers on if the exhaust flow is only going to be choked further down the line.
Headers will provide the biggest gains to cars and trucks equipped with cast-iron log-type exhaust manifolds. A log-type manifold is just a big tube bolted to the exhaust ports to collect the exhaust gas. It doesn't take up a lot of space in the engine bay and does the job of getting the exhaust gas back to the exhaust pipes, but it doesn't do much for performance because all the exhaust pulses dump into the same space. On a V8 engine, one cylinder on each bank fires within 90 degrees of crankshaft rotation of another cylinder on the same bank. These two cylinders exhaust almost simultaneously into the tube. When the exhaust gas has to compete for space in the manifold, restrictive back pressure is the result.
An exhaust header has individual tubes for each exhaust port, allowing each exhaust pulse to flow unobstructed from the cylinder head. However, some factory exhaust manifolds also have individual tubes. The most sophisticated of these and the most well thought out of this type are found on performance cars. Cars with individual runner manifolds will not benefit from headers as much as those with the log-type manifolds, but that doesn't mean they can't be improved upon. Tubes on headers are usually larger in diameter than the runners on an exhaust manifold, plus header tubes are mandrel bent to ensure the opening of the pipe stays the same radius at points where it curves. Once again, the goal is to reduce restriction and increase flow, but headers have still another benefit.
Well-designed headers produce a "scavenging" effect. When an exhaust gas pulse exits a header tube into the collector, a negative pressure wave is created that travels back up the header tube to the exhaust port during valve overlap. This negative pressure helps pull any remaining exhaust gas from the cylinder and also helps draw the incoming intake charge into the cylinder. This, of course, is very beneficial to engine performance but the tubes must be long enough for it to be effective during a useable rpm range. This brings us to our next topic, header types.
The aforementioned scavenging effect is most pronounced on long tube headers. However these headers are usually more expensive, the most difficult to install, and take up the most space. Long tube headers require that the exhaust pipes be cut and flanges attached where they join with the header collector. The benefit is increased power at sustained high revs, making them ideal for racetrack use. If you've got a late model American V8 performance car, we offer street-legal BBK Full Length Headers (stainless steel with ceramic or chrome finish) and Flowmaster's Scavenger Series Headers (stainless steel with ceramic coating standard). For select Honda and Hyundai models with higher-revving engine designs, there are the ARK Performance R-Spec Headers. Skunk 2's Alpha Series Stainless Steel Race Header is designed for Hondas and Acuras that see both racing and street use.
And if you've built a performance car that only sees track use, the Borla XR-1 Stainless Steel Long Tube Header is built for use only on vehicles with other performance upgrades, and is meant to run without catalytic converters attached. Weapon-R also offers stainless steel long-tube headers for popular 4-cylinder track built cars without catalytic converters.
Pipes on "short" tube headers are still of decent length, but they're usually not long enough to create the full scavenging effect generated by long tube headers. Before you discount short tube headers completely, they do boost power and they do fit more easily into modern engine compartments - a real benefit on newer vehicles that lack the long front end and spacious under hood clearance of yesterday's cars. Plus, many short tube headers are designed to connect to existing exhaust pipe flanges, making cutting or welding unnecessary. The diameter size of the header tube also affects flow and scavenging - larger tubes are generally better for high rpms, and smaller tubes excel at maintaining exhaust gas velocity for low-end torque.
For starters, there's Borla's Stainless Steel Header for new and old American performance cars as well as inline-cylinder Jeeps and imports. For select late-model Chevy, Pontiac, Ford, and Chrysler V8 engines, we've got Magnaflow stainless steel headers with ceramic coat standard and BBK Tuned-Length Exhaust Headers. If you've been struggling to find headers for a 1994-96 Chevy Impala SS, BBK makes them in either silver ceramic or chrome. And if you've got a Jeep Wrangler, specialist Rugged Ridge offers performance headers in a choice of finishes depending on model year.
AFE's Twisted Steel Headers are created specifically for a variety of Jeeps and select imports, and Agency Power's stainless steel headers are offered for a variety of German and Japanese brands that are most often found on tracks or street performance driving. They also include Subaru and Porsche boxer engines. If you've got a turbo engine originally built by Mitsubishi, Subaru, or Nissan, check out DC Sports' Polished Stainless Steel Turbo Manifold. DC Sports builds headers for other popular 4- and 6-cylinder domestic and Asian brands as well. There's also the Spec-D Exhaust Header for Acura, Honda, and Mitsubishi-built engines, as well as select Ford 5.0 applications.
Layout of headers is easy to determine just by looking at them. Most headers are of the "4 into 1" design, where all 4 pipes end together in the collector. On V-6 engine applications with 3 pipes per side, the expression "3 into 1" would apply to this type of layout. Another style of header pipe layout is the "Tri-Y" design. On a tri-y, opposite cylinders in the firing order are paired in a short "Y", then multiple Ys combine in the collector. Tri-Y headers increase the scavenging effect and provide a wider powerband.
With the exception of BBK's value-priced traditional steel headers, everything we offer is built from stainless steel. Because traditional steel headers won't last long without a coating that effectively resists corrosion from moisture and high engine temperatures, those from BBK we sell are finished with your choice of chrome or durable ceramic. Beware of budget steel headers available elsewhere on the internet that come only with a coat of regular paint on them. That paint is just something to keep them from rusting in the box, and they must be re-painted with high temperature paint before they are installed. Even that kind of paint won't last however, and they must be periodically recoated to avoid rust. BBK's traditional steel CNC-Series Performance Exhaust Headers are built for mainstream brands and models, and their Premium Series Headers are designed for V8 engines from Ford and Dodge Ram trucks. Gibson Performance Headers are available in both stainless steel and traditional steel with chrome or ceramic coating for American 6- and 8-cylinder engines, as well as Toyota trucks.
Stainless steel headers will not rust but they will usually turn blue near the head flange. Ceramic coatings are durable and can withstand higher temperatures. A quality set of headers will have a substantial head flange to prevent exhaust leaks and all connections will have high-quality welds. Finally, an engine works as a system, so the effectiveness of individual components is very dependent on the other parts. While long tube headers are generally better for maximum performance than short tubes, the amount of power increase either type can provide depends on the camshaft design, intake system, cylinder head ports, and how restrictive the stock exhaust manifolds are. In general, a quality set of headers should provide an increase of approximately 10-20 horsepower, and if you're restrained with your right foot, you may even see an increase in fuel mileage.
Once the make, model, and year of your vehicle are provided in the Product Options field, you'll see the specific engine choice or choices each header is designed to fit. If a choice between stainless steel or traditional steel exists, you'll see it there as well. And finally, all available finishes such as polished bare metal (for stainless steel), chrome plating, or ceramic coating will be presented for selection.
Headers are not the least expensive engine modification you can make; nor are they the easiest accessory to install. You will, however, be knocked out by the performance improvement AND the good looks they bring to your engine compartment!