Ford Mustang Four Valve Motor Upgrade Setups - Now You're Cookin' - Tech

In Our last issue of MM&FF, we brought you a few different 4.6L Two-Valve power recipes, ranging from 400 hp to 700 hp ("Force-fed Foursome"). In keeping with this theme, we decided to follow up with even more recipes for the spicy Four-Valve Cobra motors. Though sharing a common displacement with their Two-Valve brethren, the Cobra motors offer improved performance thanks mostly to a set of Four-Valve cylinder heads.

The improved breathing potential allowed for a solid 50-60 hp over the Two-Valve version in stock trim. The performance gap only increases at elevated power levels, as it's much easier to reach a given power output with the Cobra motor. Even in ported form, the Two-Valve heads are simply no match for the Cobra motors. Of course, having a pair of extra cams allows for more adjustability, plus the intake system on the Four-Valve motor is better as is the factory steel crank.

It's possible to upgrade the Two-Valve motors with the Cobra components, but this article will focus on Four-Valve power. Coverage on the Two-Valve motors began with the 400hp level, so we thought it would be a good idea to start there with the Four-Valve motors as well.

Where all of the Two-Valve combinations relied on some form of forced induction, producing 400 hp from a normally aspirated Four-Valve motor is not only possible, it's commonplace. Equipped with nothing more than Comp XE262AH cams and headers, our normally aspirated '03 Cobra motor produced 426 hp. Any decent Four-Valve combination equipped with aftermarket performance cams (the XE262AH cams were the smallest offered by Comp) and especially ported heads will easily produce 400 flywheel horsepower.

Knowing this, we stepped up with the 400hp combination and managed to produce 483 hp and 375 lb-ft of torque by combining an SHM 4.6L assembly (forged reciprocating assembly, ported heads, and Stage 2 cams), with an FR500 intake from Ford Racing Performance Parts. This combination maximized high-rpm power and allowed the 4.6 to produce peak power at 7,400 rpm (the highest of any of the combinations). In addition to the 400hp normally aspirated combination, we have included supercharged, turbocharged and even nitrous setups. In fact, two of the motors combine supercharging and nitrous oxide, demonstrating the potential of well-tuned, multiple power adders. Check out the various combinations and know there are obviously other successful recipes. Regardless of whether you choose turbos, a supercharger, or nitrous, the important thing is to get cookin'.

400hp 4.6l Four-Valve
The Four-Valve Cobra motor supplied by Sean Hyland included forged rods and pistons along with the factory forged-steel crank. Though this beefy reciprocating assembly prepared the short-block for additional power, the real performance came from the ported Four-Valve heads, Stage 2 cams and the FRPP FR500 intake manifold. Designed as a dual-stage intake, the short runners in the FR500 intake allowed the motor to produce peak power much higher in the rev range than a stocker. While the peak torque output of 375 lb-ft is about what you would expect from a suitably modified modular motor, shifting the torque curve allowed the Four-Valve motor to produce peak power at 7,400 rpm. Combining the SHM 4.6 Cobra motor with the FR500 intake resulted in an impressive 483 hp.

500hp 4.6l Four-Valve
While The '03 Cobra motor originally came equipped with an Eaton supercharger, it was replaced for this test with an '01 Cobra intake manifold to allow the motor to run normally aspirated. The '03 Cobra motor was equipped with a set of Comp XE262AH cams, a set of Hooker headers, and an Accufab oval throttle body. The big power adder on this combination was a set of NOS NOSzles that allowed direct nitrous into each cylinder via the injector holes. Basically sandwiched between the factory injector and the injector hole, the NOSzles combined the necessary fuel and nitrous delivery to each cylinder. Equipped with a 125hp jetting, the modified (normally aspirated) '03 Cobra motor produced 547 hp and 526 lb-ft of torque. There are many other ways to achieve similar power levels, including running the factory or nearly any aftermarket blower at street boost levels, but this unique Cobra combination equipped with the trick NOS NOSzles dared to be different.

600hp Zex '03 Cobra Four-Valve
By Now we all know that the factory '03-'04 Cobra motors will withstand a great deal of abuse. In one of the hundreds of tests run on the '03 Cobra motor supplied by FRPP, the crate motor was upgraded with a set of DUB pulleys (7.5 crank and 3.2 blower), a set of Hooker headers, and an Accufab throttle body. The crate motor retained the stock heads, cam, and blower/intercooler assembly (run with ambient dyno water during testing). The blower motor was further upgraded with a Zex wet EFI nitrous kit that allowed the supercharged mod motor to produce 636 hp and 636 lb-ft of torque. The addition of nitrous to the '03 Cobra motor offset the flow limitations of the factory supercharger. Given the impressive power potential of the Cobra motors, it's possible to produce over 600 hp without the aide of nitrous. All it takes is spinning the heck out of the stock blower or swapping over to one of the many aftermarket blower or turbo upgrades available.

700hp Kenne Bell SC 4.6L Four-Valve
Producing 700HP from a 4.6 Cobra motor is a simple matter of improving the efficiency of the stock motor and adding a more efficient supercharger. Despite being factory equipped with a supercharger, there's a limit to the power available from the Roots-style blower. Companies like Kenne Bell saw the opportunity to upgrade the factory blower with a considerably more efficient twin-screw version. Offering both more efficiency (more power and lower charge temp per pound of boost) and greater displacement, the Kenne Bell twin-screw supercharger upgrade has the capability to produce 1,000 hp (with the 2.8L H-series blower on a suitably modified Cobra motor). Before adding the Kenne Bell blower, the '03 Cobra motor was upgraded with a set of Comp XE262AH cams, Hooker headers, and an Accufab throttle body. Equipped with a 3.5 blower pulley and 6.5-inch crank pulley, the Kenne Bell produced 16.8 psi and allowed the '03 Cobra motor to produce 709 hp and 610 lb-ft of torque.

800hp Vortech 4.6L Four-Valve
Things Start to get serious at the 800hp level, so the '03 Cobra motor was upgraded with a set of TEA-ported FR500 cylinder heads, a set of the usual XE262AH Comp cams, and an '01 NA Cobra intake manifold. The '01 intake replaced the factory '03 intercooler assembly, as this supercharged combination was run sans intercooling. Combining the long-runner '01 intake, the modified '03 Cobra motor and the efficient Vortech T-Trim supercharger resulted in some serious power. Pullied to produce a maximum of 18 psi of boost, the supercharged Cobra motor pumped out 815 hp at 6,600 rpm and 663 lb-ft of torque at 5,900 rpm. It should be noted that use of the '01 intake improved the power output of this combination by as much as 75 hp over the supplied Vortech upper intake/stock '03 Cobra intercooler. Credit the runner length for the improvement, as the Vortech plenum/stock lower intercooler assembly relied on basically no runner length, though the '01 intake does eliminate the intercooler (a requirement at this boost level). A remote-mounted intercooler with the factory '01 intake would be the ideal choice here.

900hp Paxton/Zex 4.6L Four-Valve
This combination came about while testing a Paxton-supercharged SHM Cobra motor. Our goal was to reach 900 hp with the 4.6 motor, but the valvesprings limited engine speed, while the six-rib belt set up limited pulley speed. To overcome these hurdles, we decided to combine a small shot of nitrous with the Paxton supercharger. The benefit was twofold, as the nitrous obviously improved the power without having to resort to more engine or blower speed. In addition to the additional power, the nitrous also provided some much-needed intercooling, as introducing a gas with a temperature of -129 degrees goes a long way toward reducing inlet temps. The SHM-supplied 4.6 included ported heads, Stage 2 cams, and an FRPP FR500 intake. The Novi 2000 kit came with a 3.5-inch blower pulley that was combined with the 6.5-inch crank pulley to produce a peak boost pressure of 16.8 psi. Running a 75hp shot of nitrous, the supercharged 4.6L produced 908 hp and 683 lbs-ft of torque.

1,000hp HP Twin-Turbo 4.6L Four-Valve
The '03 Cobra crate motor was equipped as it had been for a number of tests, with a set of Comp XE262AH cams, an '01 Cobra intake manifold, and Hooker headers. Rather than rely on the factory air-to-water intercooler, the twin-turbo system from HP Performance included a front-mounted air-to-air intercooler. The use of this intercooler allowed us to utilize the factory '01 intake manifold. The available runner length is one of the reasons why this twin-turbo motor posted such impressive torque numbers (over 900 lb-ft). Running the boost up to 20 psi resulted in peak power numbers of 990 hp (just missing 1,000) and 912 lb-ft of torque. These are big numbers given the minor mods to the '03 Cobra motor, the street-oriented 57mm turbos, and a ceiling of 20 psi of boost.