Muscle Mustangs & Fast FordsHow To Engine
2003 Ford Mustang Cobra Upgrades To Crowers Cams
2003 Ford Mustang 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.
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.
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?
With the baseline power numbers generated with the stock Cobra cams, it was time to install the Crower combo. Given that our test subject was a modified supercharged street Cobra, we selected the Stage 2 (PN 62822-4) designed specifically for supercharged applications. The Crower Stage 2 cams offered 222 degrees of both intake and exhaust duration at .050 along with .475 lift. This compares to a 186/194 duration split and .392/.390 lift split for the factory 4V cams (according to literature supplied by Crower).
Obviously, installation of the cams was somewhat more difficult than your typical 5.0 Ford, but remember the Mod motor DOHC cams are located on the top of the motor rather than tucked down into the belly like a 302. It is necessary to remove the valve covers, front cover and damper for access to the primary and secondary timing chains and care must be taken when removing the stock cams. The proper spring compressor must be used to remove the rockers lest cam tower deflection rear its ugly head (the author speaks from experience here). The Crower cams went in without a hitch and it was off to the dyno again.
The supercharged 4.6 was run once again on the DynoJet in the same configuration, with the only change being the installation of the Crower cams. The data logging indicated a slight drop in boost with the cams--always a good sign that efficiency has improved. The cams made enough of a difference that minor tuning was necessary to duplicate the 11.7:1 air/fuel ratio curve achieved with the stock cams. Once thus tuned, the power output of the supercharged Cobra motor increased to 681 hp while the torque peak jumped to a 690 lb-ft. Measured peak-to-peak, the Crower cams improved the power output by 33 hp and torque by 23 lb-ft.
As a testament to the effectiveness of the cam profiles, the power output improved across the board, from 3,000 to 6,200 rpm. The torque production with the Crower cams exceeded 600 lb-ft all the way past 5,900 rpm (a gain of 400 rpm over the stock cams). Even way out at 6,800 rpm, the Crower cams allowed the motor to produce 656 hp.
I guess it is safe to say that there is power to be had by changing the factory '03-04 Cobra cams.
Replacing the stock cams with (in this case slightly) wilder cam timing can be worth additional power. Often as not, the extra power gain somewhere in the curve is offset by a power loss elsewhere in the curve. Fortunately for Cobra enthusiasts, installation of the Crower Stage 2 cams in our test motor suffered no such trade off. The power improved from 2,900 (the lowest test speed) to 6,800 rpm. Peak-to-peak the gain measured 33 hp, but the Crower cams offered a measurable power gain across the board.
While we had such an impressive test motor at our disposal, we decided to take the guys at Kenne Bell up on their offer to test a new '03-up Cobra blower upgrade. The standard Cobra blower upgrade comes with a 422 twin-screw (Autorotor) blower. Capable of serious power (we've made well over 600-wheel hp), the 422 blower is head and shoulders better than the stock Eaton in terms of power potential.
Like any good force-fed Ford fanatic, the gang at Kenne Bell knew that even though the 422 represented a huge leap in performance over the stock blower, there will always be enthusiasts looking for that much more. It was for these enthusiasts that Kenne Bell designed the 424 blower upgrade for the '03 (and later) Cobras. Capable of even more power than the 422, we decided to see just what the larger 424 was capable of.
After running Crower cams and the 422 blower, the guys at Kenne Bell swapped out the 422 and installed the larger 424 blower upgrade. The upgraded blower was installed with the same pulley combination used on the 422 (9.25-inch crank and 3.0-inch blower). The Accufab inlet and throttle body we retained, as was the 90mm mass-air meter and Kenne Bell cold-air intake system.
Swapping on the larger blower upped the maximum boost pressure from 25.6 to 29.6 psi helping the peak power jump to the magical 700 mark. Once again, the torque production was now beyond impressive, with the supercharged Cobra now thumping out and incredible 749 lb-ft at 4,100 rpm and over 700 lb-ft from 2,900 to 4,900 rpm. According to Kenne Bell, there was still over 2.5 inches of vacuum present in the intake tract, meaning there was a restriction somewhere at this elevated power level. They felt that possibly a larger throttle body or further revisions to the throttle body entry may free up some additional power at this boost level.
Equipped with the Crower cams and 424 blower upgrade this (street driven) supercharged Cobra (weighing a portly 3,780 pounds with driver) managed to rip off a best of 10.19 at 142 miles per hour. Pretty impressive numbers from a full-dress Cobra.