Can bolting on a set of headers really be worth over 100 hp?
It's no secret that there is plenty of power hiding in your exhaust system, especially with the right set of headers. But often the question is how much power is there to unlock. At times there can be as much as 100 hp or more. But all that from a simple header swap? Now that we have your attention, it's time to dig deep into some header theory, and then follow up by getting our hands dirty installing not one, but three, sets of long-tube headers on a 5.4L mod motor. Not on just any mod motor, but an all-aluminum monster chock full of modifications that (as our testing will reveal) made the combination very sensitive to changes in the exhaust system.
The idea was a simple one--run the 5.4L mod motor with the factory GT500 exhaust manifolds feeding a set of 2½-inch exhaust tubes, then follow up by testing a set of 1¾-, 1 7/8-, and finally 2-inch long-tube headers from American Racing. Not only would this demonstrate the worth of aftermarket headers in general over the factory exhaust manifolds, but also the specific gains offered by the different sizes. To make things even more interesting, we plan to follow up with the same test on a supercharged combination.
Our test engine consisted of a highly modified 5.4L mod motor. The combination started out
Oddly enough, the opportunity for this test came about from the buildup of this particular 5.4L motor. The guys at Dynatek Racing had the crazy idea to build what they call a GT1000. I figure this was a great opportunity to not only verify the four-digit power numbers of the GT1000 motor, but also run some header testing along the way. Would the headers offer more power once we installed the blower? On the surface, this seemed to make sense. After all, wouldn't more power require more exhaust flow? As we soon found out, the theories were all thrown out the window, but it must be said that all data is good data, even when it has you leaving the dyno scratching your head.
Before going any further, thanks to American Racing for supplying three sets of stainless headers for our modular application. American even went so far as to build a set of custom 2.0-inch headers for the 5.4L, but don't ask them for a set for your GT500, as fitment has not been confirmed, and the company has no intention of doing them as regular production headers.
To maximize airflow, the forged rotating assembly was topped with a set of CNC-ported Ford
The first order of business was to get the GT1000 motor assembled. Since the goal was 1,000 hp, the best way to achieve a specific power goal on a supercharged motor is to start with a powerful normally aspirated combination. To that end (and to shed a few unwanted GT500 pounds), the GT1000 started life with an aluminum Ford GT block.
The GT block was treated to precision machining and stuffed with an array of forged internals. The stock-stroke, steel crank was run with a set of forged rods and pistons to produce a seriously stout bottom end. Unlike the factory GT500 and Ford GT 5.4L motors, this GT1000 was equipped with high-compression pistons.
While Ford saw fit to run the static compression of its pair of wonder mods near 8:1, extra power was available by increasing the static compression to a full 10.0:1. In addition to the increase in power (roughly 3-4 percent per each point in compression), a 10:1 motor will get better fuel mileage than its 8:1 counterpart. Not that someone running a GT1000 is likely to worry about such things, but it's always nice when you can combine more power with better fuel efficiency. The short-block was finished off with a GT500 oil pump and pan assembly, and was ready for the power producers.