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.
Long Tube Headers
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 Exhaust 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, Borla’s XR-1 Long Tube Headers are built for use only on vehicles with other performance upgrades, and are 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.
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.
Short Tube Headers
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.
Additionally, 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 the Magnaflow stainless steel Ceramic Coated Performance Header and BBK Tuned-Length Shorty Headers. If you've been struggling to find headers for a 1994-96 Chevy Impala SS, BBK makes them in with silver ceramic coating. 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.
Header Pipe Layout
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.
Metals And Finishes Used In Header Construction
While most of our performance headers are made from stainless steel, we also offer choices crafted from traditional steel, cast iron, and titanium. Check boxes along the left side of the screen on the home page allow you to narrow your search.
When it comes to corrosion resistance, stainless steel is a good long-term investment. While stainless steel headers won’t rust, they often turn blue near the head flange if subject to prolonged heat exposure. For engines that will be run at high rpms and high temperatures for sustained periods of time, stainless steel construction with ceramic coating is recommended.
If you’re looking at traditional steel headers, choose one with a coating that effectively resists corrosion from moisture and high engine temperatures. Most of the ones we sell are finished with your choice of chrome or durable ceramic that can be selected in the Product Options field.
It’s important to remember that painted steel headers will need to be recoated from time to time to avoid rust. If you prefer to add your own high-temperature coating, you may want to consider an “uncoated” header. Ceramic coating is best suited to high heat applications.
BBK's traditional steel CNC-Series headers are built for mainstream brands and models, and their Premium Series Swap Headers are designed for V8 engines from Ford and Dodge Ram trucks. Gibson Performance Exhaust 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.
Cast iron headers offer the advantage of lower cost, and are available for select vehicles. While cast iron is heavier than other materials, it soaks up heat better – a plus for emissions, and it prevents unwanted heat from radiating onto other nearby components. Hooker’s Performance Exhaust Manifold is available for late-model GM V8 performance models, and the Drake Off-Road Exhaust Header Kit is available for Jeep Wranglers through 2006.
Often found in aeronautic parts and jet engines, titanium offers the benefits of lighter weight and higher strength compared to stainless steel. Additionally, titanium can withstand very high temperatures and is naturally corrosion-resistant. As you might imagine, headers made of titanium are a natural choice for high-performance racing applications. We’ve got the Blox Racing K-Swap Exhaust Header, B Series Hi-Flo Exhaust Header, and MaxFlo Series Tri-Y Exhaust Header for Acura/Honda models, and the Blox Racing Titanium Exhaust Header for 2013-on Subaru BRZ/Toyota 86 models.
Regardless of the material you choose, 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.
What Do “CARB-Compliant” and “EPA-Compliant” Designations Signify?
In our Performance Headers section, check boxes allow you to see products that are either “CARB compliant” or “EPA compliant”. “EPA compliant” components meet federal emissions standards set by the United States Environmental Protection Agency. These will get you through emissions tests in all states except those following more stringent standards set by the California Air Resources Board (CARB). If you’re not sure which set of emissions regulations your state follows, contact the state motor vehicles division to find out. If you live in a CARB-following state, you’ll need to select exhaust components that are “CARB compliant”.
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!