Richard Holdener
December 18, 2006
Flow Numbers: '96 4.6L {{{GT}}} (Non-PI) Head
LiftStockFPS
 INT/EXHINT/EXH
0.{{{100}}}46385554
0.{{{200}}}8479106105
0.{{{300}}}115111151150
0.400140123179170
0.500162123201178

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.