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Headers are great bolt-on speed parts that deliver good bang-for-the-buck performance. Making an engine flow exhaust better lets you pump more air and fuel through it, which will build horsepower. This is true as long as there are no bottlenecks on the induction or exhaust side of the engine. Most headers are simple bolt-up components. While it can take some time to install them, depending on the vehicle, they're great additions to your exhaust system. Headers are one of the top performance parts added to vehicles.
Header Options
Mild Steel
The most popular header material is mild steel. Mild steel is the most common material used, typically shipped with a black coating to slow down corrosion. While mild steel is usually the cheapest type available, it typically has the shortest service life.
Stainless Steel
Stainless steel headers last much longer and they look great too due to the material's corrosion-resistance properties. However, they can be considerably higher in price and turn blue/purple from heat, usually near the flange where the heat is the greatest.
Ceramic Coating
Ceramic coatings help lengthen service life when added to both mild and stainless steel headers as well as look great under the hood of your vehicle. Ceramic-coated headers also reduce engine bay temperatures and increase exhaust gas scavenging, which can produce a bump in performance.
Primary Tube Size
The primary tubes are the individual pipes on a header that expel gasses for each cylinder to the collector. The length of these tubes is a tuning factor, but so is the diameter of the tubing. All header manufacturers will state the primary tube size in inches of each design and although it goes against common hot rod lore, bigger is not always better. Typically a streetcar under 400 cubic inch will perform best with a 1 1/2" to 1 5/8" primary tube because the low RPM scavenging will offer higher torque production. For larger (400+ cubic inch) streetcar engines the best selection would be between 1" and 2" primary tube diameter. If selecting a header for a race car, typically 1" to 1 7/8" is used under 400 cubic inches. For race engines larger than 400 cubic inch engines, 2" to 2 1/4" is common practice. The main thing to remember is that a smaller primary tube will provide more low RPM air velocity for scavenging, thus more torque whereas a larger tube will provide more high RPM air velocity, thus more horsepower. The real art in selecting a header is to choose a design that is the least limiting for both low-end torque and high RPM horsepower production.
Header Design Types
Headers come in different lengths. Depending on the engine compartment and application, you may choose one over the other. If your car is equipped with oxygen sensors, when upgrading to performance headers, you may need to extend the sensor wires to reach them if the fitting is farther away. Below are the different types of headers to choose from.
"Stepped" Primary Tubes
For some time now a few manufacturers have offered a "stepped header". This design involves using a mix of different pipe diameters on the primary tubes to get the best of both worlds. As mentioned above the goal is to find the header that offers the most for low and high RPM performance. The stepped primary design typically does offer more performance gains than a conventional single sized primary, especially for streetcars. The only downfalls are that the fitment applications are limited and the price tag is typically higher since more labor is involved in their construction.
Equal Length
Equal-length long tube headers typically perform better over the other types. This is due to each primary tube being of the same length, allowing gas from all engine cylinders to travel the same distance to the exhaust, making flow more uniform. However, Equal-length headers are not as easily available as other types.
Shorty
Shorty headers are a "compromise header". Shorties are generally easier to install than long tubes but don't usually perform as well. They are meant for tight engine compartments where cross members, linkage, or other obstacles make long tube headers difficult to install. In many cases they are used as they will bolt in place of manifolds, reducing the amount of work required to make them work.
Application-Specific/Direct Fit, Universal or Custom Headers
Many of today's cars have application-specific (direct fit) headers from several manufacturers available. Direct-Fit headers are made for a particular vehicle so they install easily on the intended model and sometimes the fit can be tight. Application-specific headers are available for a wide range of vehicles going back to popular muscle cars of the '50s and '60s. If you can't find application-specific headers, contact JEGS for help in finding a set that fits. Universal headers like block huggers are a one size fits all. They are made to fit an engine and then you'll run custom exhaust from there. You can also choose to build your own custom headers.
Header Bolts
There are many header bolt options to choose from. Header bolts are available in plated steel, black oxide, and stainless steel. Many times there isn't much room to get a socket on a hex head header bolt, requiring the use of an Allen head/internal hex style of bolt or a compact head which allows a smaller wrench or socket to be used. For example, a common header bolt size is 3/8". A standard 3/8" bolt would require a 9/16" socket. A 3/8" compact header bolt usually allows for a 3/8" socket, providing additional "wiggle" room. There are also combination bolts where the outside is a compact socket style and the inside is a hex head. To prevent header bolts from loosening, some bolt manufacturers offer special header bolts that won't back out with the use of a uniquely-designed locking tab.
Engine & Header Mounting Flanges
A header mounting flange is a good indicator of the quality of a header. Up to a point, the thicker the header flange, the better. Keeping headers sealed at the exhaust ports is troublesome with a flimsy flange. The header flange will have bolt holes drilled to fit a particular engine or cylinder head. While we're talking about mounting headers, choose a good quality exhaust header gasket to save you time, energy, and money from having to replace a lesser-quality header gasket.
