Richard Holdener
July 1, 2009
Next on the list was a set of 1 7/8-inch headers. Equipped with these American Racing headers, the supercharged 5.4L produced 658 hp and 580 lb-ft of torque.

Now, is this insensitivity to the different header configurations a function of the boost from the blower (less likely), or the significant change in runner length (more likely) going from the Cobra R intake (in normally aspirated trim) to the supercharger intake (almost no runner length)? The only way to find out is to run the header test again on the normally aspirated 5.4L with the short-runner blower intake and no blower, or to run the same test on the 5.4L equipped with a centrifugal supercharger and the long-runner Cobra R intake. That my friends will be a test for another day, but this test does reveal that headers are a worthwhile upgrade on your supercharged mod motor.

Not content to leave you with just one test, we decided to run the headers versus the stock manifold one more time at a higher boost and power level. Off came the stock M122 and on went the Kenne Bell 2.8L H-series blower. The Kenne Bell blower was installed with a Mammoth blower intake, a dual 75mm throttle body, and 3.25-inch blower pulley. Run with the stock exhaust manifolds and 2.5-inch exhaust, the supercharged 5.4L motor produced 753 hp at 6,500 rpm and 619 lb-ft at 5,400 rpm at a peak boost reading of 14.1 psi. Available dyno time did not allow us to run all three different headers on this configuration, but installation of the 2.0-inch headers resulted in a drop in boost pressure from 14.1 psi to 11.4 psi, and a jump in peak power to 788 hp at 6,500 rpm and 645 lb-ft at 5,400 rpm. It's interesting to note that the headers offered almost exactly the same power gains at this power level as they did with the stock blower (33 hp versus 35 hp). This illustrates once again that the gains are less about absolute flow and more about scavenging. It should be noted that the power curve was climbing rapidly at our shut-off point of 6,500 rpm, but we felt that was a safe redline for the long-stroke combination.

The final test run with the stock supercharger was with a set of custom 2.0-inch headers. The largest-diameter primary tubes produced the highest peak power numbers of 663 hp and 583 lb-ft of torque. The peak boost numbers registered with all of the headers was consistent at 7.2 psi.

With our header test complete, it was time for Dynatek's GT1000 motor to earn its name or die trying. What we needed was more boost, so off came the 3.25-inch blower pulley and on went the 2.75-inch version. This was coupled with the larger 7.8-inch crank pulley (up from 7.1 inches) from Innovators West. This provided a drive ratio right near 2.84:1. This same ratio can be achieved with the 2.5-inch blower pulley and the stock crank pulley, but decreasing the blower-pulley size increases the chance of belt slippage. To ensure we had adequate fuel delivery, the dyno fuel system was augmented with a Kenne Bell Boost-a-Pump; likewise for the ignition system. We employed a Kenne Bell Boost-a-Spark to amplify the voltage to the MSD coil packs. This combined with the Autolite race plugs (gapped down at 0.020) resulted in zero misfires. With a crankcase full of Lucas 5W-30 synthetic oil and a fuel tank full of Rocket Brand race fuel, Westech's Ernie Mena manned the FAST controls at a peak boost pressure just north of 23 psi. Even running conservative air/fuel and timing values, the peak numbers easily exceeded 1,000 hp, the best being 1,036 hp with a new Street Rod induction system in place of the Mammoth and dual 75mm throttle body. With over 1,000 hp and 865 lb-ft of torque, the supercharged 5.4L was now officially the GT1000!