Let's face it, modular Ford owners do not look lovingly at their engine bay when it comes time to swap cams. At the very least, most view the process as time consuming and technically challenging, if not overwhelming. While there is no way to overcome the time required to swap out four cams (in the case of a Cobra engine), don't let the technical aspect steer you away from the benefits of replacing your stock cams. The critical points in the modular cam swap included putting the engine at TDC, and lining up the cam marks on the timing chains and sprockets. Though there are more cams and sprockets to line up, this really is no different than any other cam swap. Once completed, you will wonder why you put it off for so long.
The real question is not whether it can be done, but whether it should be done. Is it really worth the time and effort to replace stock cams in the Four-Valve engine? The only way to determine the benefits is to try it. For good measure, not only did we test a set of Four-Valve cams on a supercharged Cobra engine, we also threw in a test on a Kenne Bell supercharger. If you're considering cams on your '03-'04 Cobra engine, chances are the next step is a blower upgrade. Luckily, we have access to a used '03 Cobra engine. Though the supercharged engine had 86,000 miles, it was in good shape and performed flawlessly during our testing.
With our test engine at the ready, we configured it on the dyno and changed a few items on the stock one, including the engine management system, the throttle-body, intake feeding the blower, and the exhaust manifolds. We ran the Cobra motor on the engine dyno with a Fast XFI/XIM management system. Westech's Ernie Mena made short work of the tuning on our engine, allowing us to dial in the timing and air/fuel mixture for each new combination. In anticipation of the elevated power levels, we also installed 65-lb/hr injectors. On the intake side, we replaced the stock throttle-body and inlet tube with high-flow units from Accufab. Polished for visual appeal, the quality Accufab pieces greatly improved airflow to the supercharger.
Swapping cams in your Four-Valve...
Swapping cams in your Four-Valve Cobra motor is a daunting task, but the power gains are worth the effort. Our test motor came from a '03 Cobra involved in an accident. The motor and trans were purchased for a swap into a '01 Cobra.
1 Sporting the factory Eaton...
1 Sporting the factory Eaton Roots (positive displacement) supercharger, the Cobra engine was run on the engine dyno with a FAST management system.
2 To eliminate any flow restrictions...
2 To eliminate any flow restrictions into the Eaton supercharger, we replaced the factory inlet and throttle-body with this inlet system from AccuFab.
When pulled from the damaged vehicle, this Cobra engine was equipped with the factory exhaust manifolds. We elected to change them out for a set of long-tubes from Hooker. Headers not only breathe better than the factory manifolds, but offer power through scavenging that accompanies the tuned runner length. Run in this configuration, with drive pulleys from South Florida Pulley Headquarters that produced just over 11.5 psi of boost, our test engine produced 538 hp and 541 lb-ft of torque.
With our baseline out of the way, it was time for the cam swap. Knowing this car was a dedicated street car (run only on pump gas) and that we had no intention of pulling the heads for a spring replacement, we opted for a set of mild Comp cams. Naturally not all Terminator 4.6L engines (or their owners) will respond to the same cam profile, so Comp whipped up no less than 10 combinations, ranging from mild replacement to maximum-effort race cams.
Among the choices were cam combos for supercharged and nitrous applications. The Comp 4V Modular engine cam listings were broken down into three series: Xtreme RPM, Xtreme XE-R, and XE-R Supercharged and Nitrous grinds. All of the Xtreme RPM cams featured 0.425 lift, with duration figures ranging from 218 degrees (at 0.050) to 234 degrees. The remainder of the Comp offerings featured a split lift of 0.475 intake and 0.450 exhaust. The Xtreme XE-R series shared 114- degree lobe-separation angle, while the supercharged and nitrous cams all featured slightly wider 116-degree lobe separation angles.
3 All testing was performed...
3 All testing was performed with a set of Hooker long-tube headers and mufflers. Run on the engine dyno at just over 11.8 psi of boost with the Accufab throttle body and long-tube headers, the otherwise stock supercharged '03 Cobra motor produced 538 hp and 541 lb-ft of torque.
4 We chose a set of XE262AH-14...
4 We chose a set of XE262AH-14 cams for the Cobra. Having had good luck with these in the past, they were chosen to allow our cam swap without requiring a valvespring change.
5 All the chains and sprockets...
5 All the chains and sprockets used on the four-valve motor might look intimidating, but just put the No. 1 piston at TDC and line up the marks on the chains with the marks on the sprockets. Make sure to reinstall the crank position sensor before installing the front cover.
6 Run with the new Comp Cams,...
6 Run with the new Comp Cams, the supercharged Cobra motor produced 572 hp and 533 lb-ft of torque. Boost dropped slightly by about 0.5 psi (no pulley changes were made).
7 With the Cobra engine now...
7 With the Cobra engine now sporting performance cams, it was time to crank up the boost. While there was more power to be had from the stock Eaton supercharger, it would ultimately become the limiting factor in terms of power production. It was replaced with a 2.8L Kenne Bell Twin-Screw.
8 It was necessary to swap...
8 It was necessary to swap the factory air-to-water intercooler from the stock blower to the Kenne Bell. The factory intercooler was surprisingly effective, even at higher boost and power levels.