Richard Holdener
March 15, 2012

A huge thanks goes to John Mihovetz for providing the necessary tools for performing the cam surgery and assistance with dialing them in. Without the valvespring compressor, custom piston stop (to precisely locate TDC), and associated components, we would never have been able to degree the cams properly.

While the main components are very similar to the Two-Valve GT motor, the Four-Valve also featured a secondary drive assembly from the exhaust cam to the intake. This secondary chain drive required a second pair of cam sprockets and a dedicated chain tensioner. The cam installation also required removal and compression of all 32 of the hydraulic lifters. In the end, the Four-Valve 4.6L cam installation was not terribly difficult, just time consuming.

The ported heads and XE262AH cams were combined with a ported stock intake, also from Sean Hyland, but no changes were made to alter the runner length of the factory intake. We also tried a larger throttle body, but at this power level, the stock throttle body seemed more than adequate.

The final performance upgrade included Hooker headers to replace the factory exhaust manifolds. Since we were looking for all the extra power we could find, the headers were a natural upgrade. After the upgrades and a tweak in the tune, output jumped to 435 hp and 409 lb-ft of torque. Not only did the upgrades improve the power output by just over 100 hp, but the torque peak was up 80 lb-ft. In fact, the power output was up through the entire rev range.

Having made all of the changes at once, we still had some daylight to burn and a healthy Four-Valve just begging for more mods. Despite not being offered by Ford Racing any longer, we decided to pull out an FR500 intake manifold we had stashed away. The FR500 is unique—not only is it made of lightweight magnesium, but it also offers dual runners. The design combined one set of long runners to bolster low-speed power with a set of short runners to enhance the top end. Unfortunately, we didn't have the actuators to switch between the long and short runners, and were instead forced to run the intake with the short runners activated. Looking primarily for peak power numbers anyway, the FR500 increased the output of the 4.6L to 483 hp at a lofty 7,400 rpm.

For the last hurrah, we added nitrous. Though a simple wet fogger system would suffice, we dusted off an old Nozzle system from NOS. We like the equal distribution offered by the individual-port system, as well as how cool the thing looks once installed. The system features individual nozzles that are positioned between the injectors and receiver holes in the intake manifold. For this test, we removed the FR500 and reinstalled the ported stock intake.

Like most systems, the NOS kit is adjustable using different nitrous and fuel jets. With jetting designed to supply an additional 100 hp, we pushed the button and were instantly rewarded with peak numbers of 547 hp and 526 lb-ft of torque. Big numbers with nitrous are so easy, just make sure you have plenty of fuel and retard the timing as we did by 3-4 degrees at this power level. Looking back at how easy it was to increase the power output of the Four-Valve, we'd say the 4.6L has a solid future in the performance industry.

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Stock vs. Modified - Graphs tell so much more than simple peak power numbers. Adding the ported heads, intake, and Comp cams to the 4.6L, Four-Valve motor offered dramatic power gains. The peak power outputs jumped from 336 hp and 332 lb-ft of torque to 435 hp and 409 lb-ft. The combination improved power output through the entire rev range, with sizable torque gains coming down as low as 3,500 rpm. Credit the time spent degreeing the cams for some of the additional power.
Modified 4.6l 4V Intake Test--Ported Stock vs FR500 - Though no longer available, we had access to one of the dual-runner FR500 intake manifolds previously offered by Ford Racing. We tested the intake in short-runner form only, meaning we were most concerned about maximizing peak power. The short-runner intake performed as expected, allowing the motor to make peak power at 7,400 rpm instead of 6,100 rpm. The result was a jump in peak power to 483 hp, though the FR500 lost out to the factory intake below 6,000 rpm
Modified 4.6l 4V-NA vs NOS Nitrous (100hp) - After removing the FR500 intake, we had one final test to run. A few years back, NOS had shipped a set of nozzles that combined the nitrous and fuel in unique fittings designed to house the factory injectors. Given the limited amount of nitrous we used on this test, the same power gains could be expected from a simple single-fogger nozzle placed in the throttle body or air intake, but we liked the even distribution offered by the Nozzle setup. After installation of the Nozzles on the ported stock intake, we ran with jetting to provide an additional 100 hp. The result was a jump from 435 hp to 547 hp, with torque up from 409 lb-ft to 526 lb-ft.