Facts About Headers

How come there is such a price difference between header brands?

Header development and design is complex and requires a substantial amount of time and resources to do the job right! Many manufacturers are unwilling to make the commitment and instead offer compromised headers at lower prices.

Doug’s will not compromise performance, quality or fit to compete with inferior designs at cheap prices. Every Doug’s header is tuned with the proper tube size and length to efficiently remove all the exhaust from each cylinder, reducing pumping losses resulting in a dramatic increases in horsepower and torque. Doug’s headers are carefully developed on the vehicles they are intended to fit and are re-checked numerous times during the design and manufacturing process.

Do all Doug’s headers have the same basic design?

No, absolutely not. Doug’s headers are designed and built to fit each applications specific requirements. The headers design is dependent on the intended vehicle usage and emissions requirements. Doug's headers utilize five types of header designs:

Full Length 4-tube header example4-tube full length headers are typically used for higher RPM horsepower, but can also increase the mid range torque in applications were there is room to fit a long tube design.
Tri-Y tri-y header exampleTri-Y headers for muscle cars, trucks and motorhomes yield maximum power from off idle to 4500 RPM making them well suited for applications demanding maximum mid-range torque with maximum fuel economy.
Manifold Replacement 4-tube stock manifold replacement header example4-tube stock manifold replacement headers are designed for easy installation and emissions compliance.
Shorty 4-tube shorty header example4-tube shorty or “clippster” headers provide improved ground clearance for popular muscle cars and street rods.
Tight Tuck 4-tube tight truck header example4-tube tight tuck headers are the best solution for narrow frame rail street rods.

How important are flange and tubing thickness to header performance?

A properly machined and finished header flange eliminates annoying exhaust leaks which lead to horsepower loss. Doug’s headers utilize 3/8” flanges on passenger car and street rod applications and 1/2” to 5/8” flanges on heavy-duty applications, such as motorhomes and late model trucks. Thicker flanges hold up to heat better and are less likely to warp. Late model vehicles and high performance muscle cars produce super heated conditions that can warp “thinner” flanges.

Header tubing thickness and proper fixture welding techniques can affect the longevity of a header. Headers for light duty applications are built with 16 gauge tubing. Heavy-duty applications, such as motorhomes or tow vehicles demand thicker 14 gauge tubing. Doug’s headers are built in heavy duty jig fixtures which eliminate heat distortion and movement of the individual header tubes. Each header is welded using cyclical welding techniques which reduces tube distortion.

What kind of performance gains can I expect by installing a set of headers?

The addition of a set of headers typically adds 15-20% more horsepower and torque.  How much performance is gained depends on the condition of your vehicle and any additional upgrades you have made to the engine (intake, fuel delivery, cam, and ignition). All of our headers are designed and tested with appropriately sized tube diameters and lengths to bring you maximum performance and engine efficiency.

How do I know what primary and collector diameter size is best for my application, when choosing a header?

The best way to determine what size is best for your application depends on the purpose your vehicle. For daily drivers or engines that reside at low RPM ranges, smaller primary tube and collector diameters provide more low-end performance. Generally speaking the larger tube and collector diameters increase your horsepower and torque at higher RPM levels and are usually recommended for street/strip or race only applications.

What modifications are necessary to make my headers fit?

Our product development department takes a substantial amount of time and effort to design our headers, so you don’t have to! With 40 years of expertise in designing, manufacturing and installing exhaust products we can offer a quality product that fits. Most of our street rod and muscle car header applications are direct bolt on applications with little welding required. Late model truck, SUV and motor home applications do require welding during installation. If you do not feel comfortable with welding operations find a professional exhaust shop to help with the installation.

What is included with a set of Doug’s headers?

Every Doug’s header comes with all the necessary mounting hardware, collector reducers or connector pipes, premium gaskets and detailed installation instruction sheets. Our extra thick gaskets are rated up to 1100ºF, pressures to 3700 psig (255 bar), and are designed for an exact port match with Doug’s headers. We do not recommend the use of other aftermarket gaskets. Doug's premium gaskets are sold separately see page number 27 for applications.

What finish is applied to a Doug’s header?

Metallic Ceramic Thermal Barrier Coating (MCTBC) is simply the best header finish on the market and comes standard on all Doug’s headers. MCTBC protects and extends the life of headers by creating a thermal barrier that significantly lowers underhood temperatures and protects the substrate metal from thermal fatigue. After MCTBC is applied, it is polished with a vibratory finishing process that produces a high luster aluminum appearance. This coating is easy to maintain and will last for years under normal operating conditions. The polishing process compresses and activates the coating, which increases the surface hardness to produce a finish that is 60% more corrosion resistant than an unpolished surface.

What should I do if I encounter an installation problem with my header?

Header installation for the most part can be accomplished with simple hand tools, a floor jack and jack stands. Some applications can be very time consuming due to limited space in the engine compartment. Should you encounter a fitment problem do not attempt to modify or alter the header in any way or your warranty will become void. Call our knowledgeable technical staff for assistance at 909-599-5955. Headers returned without prior written authorization will be refused. Read our complete warranty policy on the last page of this catalog.

Do you build custom headers?

We do not custom build headers.  However we do offer a complete line of do-it-yourself components for fabricating your own headers and exhaust systems. A full assortment of smooth wrinkle free mandrel bends (45, 90 , 120 ,180 degree) and straight tubing, as well as header and collector flanges and gaskets are available at affordable prices. We do offer some pre-bent weld-up kits for race car and street rod applications.  We do work with many custom fabricators around the country and may also be able to recommend someone in your area. Please download our 2008 Patriot catalog for a complete list of available components.


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