Cylinder Head Install - Project Redheaded Step Child Part 6

200,000-mile 4.6 vs. CHP/FPS 4.6
Swapping out the original 4.6 for the new version was worth some serious power. With over 200,000 miles logged, the original engine was getting a little long in the tooth. Despite our best efforts, the thing just didn't seem to want to make enough power. After posting 235 hp at the wheels, the motor was removed and put down 264 hp at the flywheel. The new CHP short-block topped with the FPS ported heads and (the same) XE262H cams increased the power output to 308 hp, while the peak torque was up to 347 lbs-ft (up from 326 lb-ft-finally a sizable power gain from all our efforts.

Cam Swap-XE262H vs. XE274H
In an effort to further boost the power output of the 4.6, we elected to swap out the smaller XE262H cams for the larger XE274H grinds. Though the two cam profiles shared the same 0.500-inch lift and 114-degree lobe separation, the XE274 cam offered an additional 12 degrees of intake duration and 8 degrees of exhaust duration. The increase in duration improved the power output from 4,100 rpm to 6,000 rpm (and beyond), but there was a slight tradeoff in power below 4,000 rpm. The cam swap netted us another 9 peak horsepower, bringing us ever closer to our 300hp goal.

Stock vs. Prototype VRI Intake
As a teaser, we thought we'd show you the effect of a new prototype intake on the early 4.6 Two-Valve motor. At this power level, the non-PI intake was definitely restricting the power output. Removing the non-PI Intake, C&L plenum, and Accufab 75mm throttle body in favor of the new VRI intake resulted in a significant power gain. The peak power jumped from 317 to 355 hp, while the torque peak was up to 364 lb-ft. The new VRI intake offered huge power gains past 5,000 rpm, but lost no power (as is usually the case) down low. Even at 3,800 rpm, the VRI improved torque production by 24 lb-ft. In fact, the prototype intake improved the power output from 3,000 rpm to 6,500 rpm.

After running the new combination...        read full caption After running the new combination with the smaller XE262H cams, we swapped in the larger XE274H ones. The result was an increase in peak power from 308 hp to 317 hp at the same 5,200 rpm. We suspected the intake was now holding us back from producing more power. A prototype of a new intake designed by the author resulted in a huge gain in power from 317 hp to 355 hp. Look for photos and a new test on a real production piece (on the chassis dyno) in a month or two as we (hopefully) eclipse our goal of 300 hp.

Before installing the more...        read full caption Before installing the more powerful combination back into the engine bay, we stepped up to a new Centerforce clutch system that includes a dual-friction disc and an aluminum flywheel. Given our plans to supercharge this combination, we know the stock clutch was not up to the task of the intended power.

Back on the chassis dyno,...        read full caption Back on the chassis dyno, the new combination increased the power output from 235 hp to 276 hp. We were inching ever closer to that 300hp mark.