Capristo Header w/ Heat Protectors Ferrari 458 Italia 10-15
Before we make your head spin on whether a header upgrade is worthy or not, we first must know what a header is.
First, we differentiate a header from an exhaust manifold that comes stock with most cars. While they do the same job, the difference is that an exhaust manifold is a solid cast iron piece across all cylinders while an exhaust header is made up of individual steel tubes for each exhaust port, welded to meet at a collector or several collectors to bring the exhaust gases down to a single pipe, ready to flow through the rest of the exhaust system.
Manufacturers use exhaust manifolds for a few reasons, but the two main ones are that cast header blocks are cheaper to produce, and the fact that these thick cast-iron structures are great for holding in heat, are very durable and help keep unwanted exhaust noise down. As enthusiasts, exhaust noises are mostly wanted.
And then we get to the disadvantages of most stock exhaust manifolds which are rough interior surfaces from casting results in poor exhaust flow and unequal length of exhaust travel for each cylinder to meet at the collector.
The first issue is taken care of pretty easily. Since exhaust headers are made from smooth bore tubing, there is very little to disrupt the exhaust flow.
Ridding you of the second issue is where things get tricky because we are going to the subject of scavenging.
Scavenging can be thought of as the opposite of backpressure. With efficient exhaust flow, the outgoing gases will create a vacuum behind the outgoing pulse. As the valves are opening between cylinder strokes, there is a sweet spot where the intake and exhaust valves are at least partially open at the same time.
Remember: more air = more power.
Where equal length headers come into play to help here, is by ensuring that each the tube from the cylinder head to the collector is the same length, those exhaust pulses have the same distance to travel to get there. That way, there is always a clear path for the exiting exhaust to free up as much back pressure as possible for the next pulse coming back down that line, ensuring as close to ideal conditions for scavenging as possible.
This is where the main advantage of headers come from, and why there is usually such a large performance benefit in installing them.
Another reminder for those who like big-bore pipes is that a bigger header tube isn’t necessarily better. The process of scavenging relies on the vacuum created in that pipe, and too large a diameter would limit that effect.
This is why engines make more power with headers on than if they just vented straight to atmosphere directly from the cylinder head.
Another reminder for tuning your car is to make the rest of your exhaust system less restrictive before you install headers. This means installing larger-diameter, mandrel-bent exhaust pipes, and it means using freer-flowing mufflers. There will be no benefit at all to putting headers on if the exhaust flow is only going to be choked further down the line.
Different style headers provide varying sounds and power. Long tube headers supply the most power and increase the vehicle’s sound. Mid-length headers give power ratios and sound qualities somewhat less than long tube headers.
Horsepower and torque is the biggest benefit to installing aftermarket headers. Another benefit is the driver’s ability to open the car’s exhaust, which generates an appealing sound.
So, to summarize: Headers improve flow, make nice noises, and add a bit of power and torque.