What do you get when you combine...
What do you get when you combine a quartet of Crower 4.6 cams with an already impressive supercharged Cobra?
Every time Ford introduces a new engine the aftermarket scrambles to come up with new cam profiles to further enhance the new motor--although in this case the scrambling has seemed more like ambling. Case in point, the supercharged '03 4V Cobra mill. While the four-valve configuration has been with us for some time now, Crower is the only one of the 3-C cam companies (Comp, Crane and Crower) to currently offer cams for the four-valve 4.6 Modulars.
Crower's offerings include everything from the Baja Beast, designed specifically for heavy truck and SUV applications to a Stage-4 race grind. Of course the offerings include all manner of custom-ground and proprietary profiles, but the off-the-shelf listings included seven different cams.
With so many different cams to choose from, naturally we had to put at least one set to the test on the dyno. Having run so many 4.6 2V tests in the past few months it was refreshing to actually run something different for a change. Besides, four-valve Cobra motors are not just different, they are impressively powerful, especially when equipped with a Kenne Bell blower.
The '03 Cobra was previously...
The '03 Cobra was previously modified with a Kenne Bell blower upgrade consisting of the twin-screw Autorotor supercharger.
Often as not, we like to perform a comparison test on a stock or near stock motor, but stock supercharged Cobras are getting harder and harder to find. Given the way they respond to modifications, it is no surprise that owners are quick to crank up the boost and improve the intake and exhaust systems. Force-fed Fords are so detuned from the factory that huge gains can be made with relative ease.
The most common route to improving the power output of a factory supercharged Cobra is to install a larger crank or smaller blower pulley (or both) to increase the rotor speed of the M112 supercharger relative to engine rpm. The increase in blower speed relative to engine speed will increase the airflow supplied by the blower, thus improving the boost pressure and power output. Obviously there is a limit to the flow (and boost) potential of the Eaton supercharger, so you can only crank up the boost so far before reaching a point of diminishing returns. Before you reach the limit of the Eaton supercharger, it is a good idea to replace the stock throttle body and address the restrictions inherent in the air intake system. Positive displacement superchargers are ultra-sensitive to inlet restrictions so make sure the blower has an unrestricted source of inlet air.
After cranking up the boost and freeing up the inlet system, most enthusiasts venture down the exhaust and tuning avenues. Actually, tuning is critical to optimum supercharged performance, so make sure the additional boost pressure is accompanied by the correct amount of fuel and that the timing curve is realistic given the octane rating of the intended fuel. Custom chips (like the one supplied by Kenne Bell via Superchips Custom Tuning Software) can be worth not only huge power gains, but they will ensure safe air/fuel and timing curves that will save your precious engine from rattling itself to death.
Exhaust mods include heads and a cat-back exhaust, but we have seen many Cobra owners forego the exhaust mods and concentrate on the boost, tuning and inlet modifications. Eventually, Cobra owners will reach the limit of the power available with the stock Eaton supercharger and then it is time to embrace a blower upgrade. We have detailed the benefits of replacing the stock Eaton supercharger with a much more efficient twin-screw unit from Kenne Bell in previous issues; we've also seen wild numbers from these cars with ProCharger swaps.
Crower supplied the necessary...
Crower supplied the necessary 4V 4.6 cams for installation into the Cobra. The Crower sticks featured 222 degrees of both intake and exhaust duration at .050 along with .475 lift. This represented a significant jump in both lift and duration over the factory 4V specs (186/194 duration split and .392/.390 lift).
While the Kenne Bell blower will allow you to make some serious power, at some point, it will become necessary to dig into the engine (though not to far) to unearth additional horsepower. Actually, installation of a set of Crower (Stage 2) cams will benefit any supercharged Cobra regardless of the state of tune. We were just trying to prepare you for our modified tester. Rather than run the comparison on a stock '03-04 Cobra plant, we decided to test them on something a little more powerful.
The test mule consisted of an '03 Cobra equipped with a Kenne Bell (422) blower. Though no internal mods were performed to the four-valve motor, the Cobra did feature some additional power-producing performance pieces. Feeding the beast was a Kenne Bell cold-air intake system. The Kenne Bell air intake system fed inlet air through the stock 90mm mass-air meter to an Accufab (single-blade) throttle body and air intake system. Given the additional power potential of the modified Mod motor, the stock injectors were ditched in favor of a set of 60 pounders fed through a 1/2-inch fuel line by a Boost-a-Pump augmented pair of stock Cobra fuel pumps. During high-boost testing, the motor was run with C16 race fuel, but runs daily on 91-octane pump gas.
With all that supercharged power forcing its way into the motor, it was imperative to get it all out as well. The exhaust system consisted of a set of Kooks headers, high-flow cat pipe and a Bassani Cat-Back exhaust system. In a quest for improved e.t.'s, the Cobra-exclusive independent rear suspension was replaced with a standard-issue solid rear axle featuring 3.55 gears. The stock tranny has held up to the abuse, but the stock clutch was upgraded with a CenterForce dual-friction setup and matching steel flywheel.
Using the new Superchips Custom Tuning Advantage software, a custom chip was used to dial in the combination. Running a combination of 23 degrees of total timing and a steady air/fuel mixture of 11.7:1, the 4V 4.6 produced peak numbers of 648 hp and 667 lb-ft of torque at a maximum boost pressure of 25.6 psi with the stock Cobra cams. As we have come to expect of twin-screw supercharged Cobra engines, the torque curve was every bit as impressive as the power curve. The KB-augmented '03 thumped out more than 600 lb-ft of torque from below 2,900 to 5,500 rpm. Imagine what 600-plus lb-ft of torque feels like at 3,000 rpm?
 After running the baseline...  After running the baseline test with the Kenne Bell-modified Cobra, out came the stock cams. |  This Horiba wide-band oxygen...  This Horiba wide-band oxygen sensor was used to monitor the air/fuel mixture during testing. When your sneaking up on 700-wheel hp, you better make sure the motor does not experience a lean condition. |  Kenne Bell employed Superchips...  Kenne Bell employed Superchips Tuning's Advantage software to optimize both the air/fuel and timing curves. |