Stock exhaust systems typically restrict the flow of exhaust gases out of your engine, and thus prevent your engine from reaching its full power potential. In our “Exhaustive Research” post, we showed you how to choose the right exhaust system to help gain back lost horsepower.
Of course, the first exhaust components to handle spent exhaust gases from your engine are the exhaust manifolds or headers. The stock manifolds are restrictive, but a set of mandrel-bent aftermarket headers will allow the exhaust gas to move freely from the engine, reducing power-robbing backpressure in the process and allowing your exhaust system to expel gases even more efficiently. A good set of headers will actually build up enough exhaust flow velocity to create energy pulses that pull or scavenge spent gases from the engine.
So what makes a good header for your application? Consider these five points:
1. Header Size: Bigger Isn’t Always Better
One of the main considerations in choosing a set of headers is the diameter of the primaries, which are the pipes that connect directly to the exhaust ports. There are many factors that go into choosing the right pipe diameter—engine size, horsepower, intended use of the vehicle, and more—but one common mistake that many hot rodders make is to assume bigger is better.
Although smaller-diameter primaries will flow less volume than bigger primaries, a smaller diameter pipe actually creates faster exhaust flow velocity with just enough resistance to foster good low- and midrange torque. For that reason, most header manufacturers recommend modest pipe diameters for street applications—1 ½-inch to 1 5/8-inch diameter primaries for a small block engine, for example.
2. Header Dimensions: Full Length vs. Shorty
Headers come in a variety of dimensions and configurations for specialty applications, including fenderwell, dragster, and circle track headers. We’ll keep our focus on the most common street performance designs: full-length, shorty, and mid-length.
Full-length headers utilize primary tubes that are longer than the primaries on your stock exhaust manifold. In most cases, these four primary tubes empty into one collector pipe and form a “4-1” design. Full-length headers help produce more overall power with good power in the low- and mid-rpm ranges—right where most street-driven vehicles can use it the most! The longer primaries also reduce the chance of escaping gases getting drawn back into another pipe.
Shorty headers consist of four short primaries that dump into one short collector pipe. The compact dimensions make shorty headers a perfect choice for extremely crowded engine compartments or lowered vehicles where clearance is a concern. Shorty headers also typically work with the remaining stock exhaust components without modification (full-length headers require some modifications), so installation is often a quick, clean process. Although shorty headers don’t always produce as much low- and mid-range power as full-length headers, they do provide significant power gains over stock manifolds and have the potential to produce higher rpm power gains.
You can maximize the performance of your shorty headers by opting for equal-length primaries. Equal-length primaries will scavenge gases equally from all eight cylinders, keeping the torque curve consistent from each cylinder. The result is a broader torque curve in the low- and mid-rpm range.
Mid-length headers offer some of the benefits of full-length and shorty headers. They provide longer primaries than the stock manifold to help produce more of that coveted low- and mid-range torque and power. However, the primaries are not as long as full-length headers, so there’s increased clearance for lowered vehicles.
3. Header Configuration: 4-1 or Tri-Y?
As we mentioned earlier, full-length headers typically use a 4-1 design to empty the primaries into the collector pipe. However, some manufacturers offer headers in a “Tri-Y” configuration.
Tri-Y headers merge the four primaries into two slightly larger secondary pipes before merging into one collector. These secondary pipes allow the exhaust gases to maintain a higher velocity for a longer period of time as they gradually merge into the collector. This enhanced exhaust flow typically results in a broader torque curve than 4-1 headers.
4. Header Material: Mild Steel vs. Stainless Steel
Most aftermarket headers are made from steel or stainless steel. The advantage of choosing a standard steel header is simple: cost. Mild steel headers cost significantly less than varying types of stainless steel but don’t offer the durability of stainless steel.
Stainless steel headers last longer than mild steel headers in extreme conditions, such as the environment in your engine compartment. They are better able to stand up to extreme heat and will not rust. The superior thermal characteristics and rust-free surface of stainless steel allows them to maintain smooth, restriction-free exhaust flow throughout their lifespan.
5. Header Coating: The Ceramic Benefit
Once you choose between mild steel or stainless steel headers, chances are you’ll be faced with another dilemma: natural vs. coated. The most common type of header coating is ceramic coating, which provides an added thermal barrier. This keeps heat inside the primaries and helps keep ambient temperatures low in the engine compartment. That means cooler, denser intake charges and increased horsepower. In addition, ceramic coated headers maintain their finish, even in extreme conditions.
Headers are also available with a natural or painted finish. These finishes are a more affordable alternative to coated headers, but don’t provide the performance or durability benefits.
No matter which style you choose, you can take full advantage of your new headers by scrapping the rest of your restrictive stock exhaust, including the mufflers—find out how to choose the right muffler now.