Richard Holdener
August 13, 2010

After backup runs demonstrated that these numbers were perfectly repeatable, the Mustang was pulled from the rollers and out came the Stage 1 cams. Having run the majority of my testing on the engine dyno, I don't envy having to perform cam swaps in the car, but the performance enthusiasts at ST Motorsports made short work of the cams, and we were up and running in no time. The Stage 1 cams were replaced with XE280PH-13 cams. The Stage 3 blower grinds (PN 127650) offer more lift and duration, not to mention a slight change in the lobe separation angle.

The Stage 3 cams feature a 0.559/0.560 lift split, a 245/256-degree duration split (measured at 0.050), and a 113-degree lobe separation angle. Unlike the NSR Stage 1 cams, these ballistic bumpsticks required increased valvespring pressure and cam phaser limiters. Lucky for us, the Livernois Stage III heads already feature sufficient spring pressure (and coil bind clearance) to work with both cams, while Comp Cams supplied the necessary Phaser limiters. The limiters are used to reduce the amount of cam phasing available, from near 50 degrees down to just 20 degrees, to maintain proper piston-to-valve clearance. Since major adjustments are made only at part throttle, little or no power is lost with the installation of the limiters at wide-open throttle.

Once the Stage 3 blower cams were installed, the GT was positioned back on the DynoJet. It was evident that these cams are more aggressive than the Stage 1 grinds. Adjustments were made to tame the idle quality, but it was obvious this car was running something other than stock sticks.

Keeping the air/fuel mixture at 11.8:1 and the total timing locked at 23 degrees, output jumped to an amazing 836 hp and 713 lb-ft of torque. The Stage 3 blower cams were worth 85 hp over the already impressive Stage 1 cams. Since this is an automatic, the start rpm was roughly 3,500 rpm, but no power loss was experienced with the cam swap in the tested rpm range.

Where the Stage 1 cams failed to reach 700 lb-ft of torque, the Stage 3 cams bettered the 700-lb-ft mark from 4,600 rpm to 6,100 rpm. Instead of falling off after 6,500 rpm, the motor pulled hard all the way to 7,000 rpm. Remember, this was a car that already ran 9.79 at 140 mph when the motor was making just 750 rwhp. The extra 85 hp should easily knock 0.30-0.40 off the e.t.'s, maybe more.

Impressed as we were with the gains offered by the Comp Cams Stage 3 blower cams, the boys at ST Motorsports weren't done yet. Installation of the Stage 3 cams actually dropped the boost pressure by as much as 2 psi, which is something we've come to expect from improving the efficiency or displacement of the motor.

Knowing they had smaller blower pulleys in hand for the 2.8L Kenne Bell, they installed a 2.5-inch blower pulley and let 'er rip. Keeping the air/fuel and timing the same as the previous runs, the motor just touched 900 rwhp and over 880 lb-ft of torque. Torque production exceeded 800 lb-ft from 3,200 rpm to 6,200 rpm, making for one serious torque curve.

From the looks of the curve, there seems to be an airflow restriction somewhere in the system. The guys at ST Motorpsorts are looking to install an even larger throttle body and follow that up with an exhaust upgrade, and then the larger 3.6L supercharger in their quest for even more Three-Valve power. For now, we are plenty impressed with any supercharged Three-Valve pumping out 900 rwhp through an automatic.

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