Richard Holdener
December 18, 2006
With nowhere else to turn, we had to yank the motor out of Project RSC to make way for a more powerful combination. Westech's Steve Abbruzzese (left) and Eugene Walde did most of the heavy lifting.

When we last left the Redheaded Step Child-our beloved high-mileage '96 4.6 GT-we had just completed the Maximum Motorsports suspension upgrade. The Stang was also blessed with a set of 18x9.5-inch Cobra R wheels straight out of the Ford Racing catalog and grippy Nitto 555 ultra-high-performance tires. This allowed the GT to canyon carve with the very best that Europe-and America-had to offer.

The only downside to the new suspension and footwear was that the elevated handling levels made the early non-PI motor feel all the more pathetic. Despite some impressive speed equipment, the most we'd been able to muster thus far was 241 hp. The peak torque figure exceeded 300 lb-ft, but the tiny mill just did not want to carry that impressive torque production beyond 4,000 rpm, where it would provide some decent horsepower numbers.

Rather than continue to throw performance parts at the thing, we decided to take drastic measures. This entailed running the 4.6 on the chassis dyno one last time with the current configuration to reestablish a baseline before removing the tired soldier in favor of something a bit more sporting.

You will remember that the idea behind this project was to build up an early, non-PI 4.6 Two-Valve engine (normally aspirated) to exceed 300 hp, all without resorting to the use of the later PI components. While the PI upgrade is probably the preferred (and recommended) route, we wanted to see if it was possible to get there with the non-PI components.

Before pulling the 200,000-mile 4.6, we ran it one final time on the SuperFlow chassis dyno, where it put down 236 hp.

In doing so, we could illustrate the gains available to owners of the early modulars who have decided to stick with their original equipment. Not everyone can step up financially to the complete PI swap, so this bolt-on route is a viable option. Having exhausted the list of external bolt-ons (with the exception of forced induction and nitrous, which are coming), we decided it was time to crack open the 200,000-mile mill. The next logical step in our quest for additional performance were the factory cylinder heads. Despite being down on flow compared to the later PI heads, the early units can be made to flow pretty well, certainly much better than stock.

With additional flow in mind, we shipped a set of early heads (the original '98 engine used in our "Mods for Two-Valve Mods" series) to Ford Performance Solutions. FPS subjected the early heads to the CNC machine and increased the intake flow rate from 162 cfm to 201 cfm. The exhaust flow increased as well, from 123 cfm to 178 cfm (all measured at 0.500-inch lift). The FPS-ported heads were also upgraded with a set of SI valves and Comp valvesprings.

With such impressive heads at the ready, we thought long and hard about installing them on our tired, weak-ass 200,000-mile short-block. What the new FPS heads really deserved was a fresh motor, capable of taking advantage of the extra flow and power offered by the CNC porting. In the end, our decision came down to rebuild or replace. Wanting to minimize downtime, we elected to replace rather than rebuild the existing combination. A call to Coast High Performance netted us a suitable replacement 4.6 block.

Not needing anything wild, the boys at CHP put together a freshly machined, iron 4.6 block stuffed with a cast crank (stock stroke) and a set of forged rods and pistons. Where the early factory 4.6 pistons featured an 11cc dish, the Probe Racing pistons upped the compression slightly with a 4.5cc dish. In truth, the change was not dramatic, as the FPS CNC porting applied to the early heads increased the combustion chamber size by a few ccs. All we wanted to do was maintain the factory compression ratio of 9.3:1, and we were rewarded with a final compression of nearly 9.5:1.

Both engines were run with Lucas 5W-30 synthetic oil, though the old motor hardly deserved a crankcase full of the good stuff.

No main stud girdle or Cobra crank was required for this application, and we have no reservations about adding nitrous or a Kenne Bell blower in the near future (tuning, as always, is the key). The FPS heads were installed onto the awaiting CHP short-block with a set of ARP head studs and Fel-Pro head gaskets. A huge thanks goes out to John Mihovetz of Accufab for coming to the rescue with a set of ARP head studs (ours did not arrive in time for the dyno testing), head dowels, and chain tensioner studs.

Before beginning the wild week of weirdness, we ran Project RSC's motor-which was equipped with a C&L elbow and Accufab 75mm throttle body, a set of BBK underdrive pulleys, and Comp XE262H cams-on the Super Flow chassis dyno. Also on board were a set of Hooker long-tube headers and off-road (no cats) X-pipe feeding what was left of our stainless steel after-cat exhaust. We had to hack and slash the system after installing the Maximum Motorsports suspension since the over-the-axle portion of the exhaust would not fit the new suspension. We retained the mufflers and fabricated a pair of turn downs to direct the exhaust flow under the rear axle. The motor also featured a BBK air intake and custom chip tuned by Power Train Dynamics. Equipped as described, the 4.6 put down 236 hp and over 300 lb-ft of torque at the wheels as measured on the Super Flow chassis dyno. Back-up runs showed the same numbers, so these became our new baseline before removing the motor.

With the help of Eugene Walde, Steve Abbruzzese, and Tom Habryzk from Westech, we had the 4.6 out in no time and installed on the engine dyno. The mill was configured for engine dyno use by removing the accessories (we ran only an electric water pump), installing the headers and collector extensions, and hooking up the FAST management system to our MSD coil packs. We took the liberty of running five fresh quarts of Lucas synthetic oil and a new oil filter, though the tired motor hardly deserved the high-quality synthetic lubrication for just a few dyno runs. Equipped with the stock non-PI intake and Accufab/C&L throttle body combo, the pathetic project powerplant pumped out an uninspiring 264 hp and 326 lb-ft of torque.

The difference between the chassis dyno numbers and those generated on the engine dyno was just under 12 percent, well under the 20 percent numbers often quoted by some engine builders, chassis dyno operators, and others. Skewing the power differences by removing the accessories, mufflers, and air intake only served to reinforce this point. There is no straight percentage difference between chassis and engine dyno numbers that can be applied to all circumstances.

Having illustrated the reality between engine and chassis dyno numbers, we removed the tired motor and proceeded to swap over the necessary components required to bring the new CHP/FPS powerplant to life. Given the 235 hp generated at the wheels on the chassis dyno, we were roughly 65 hp away from our goal of 300 hp. We were hoping the new short-block and ported heads would take us at least most of the way there.

Run on the engine dyno, the tired 4.6 produced 264 hp at 4,800 rpm and 326 lb-ft of torque at 3,800 rpm.

Our expectations of the new configuration were further increased by the fact that a compression test of the original 4.6 revealed one extremely weak cylinder. Off the original motor came the oil pump, pan, and pickup, along with the cam sprockets, chains, and tensionsers. Also part of the swap were the XE262 cams, stock lifters, and valve covers. Additional carryover items included the intake and throttle body, the front cover, and, naturally, the headers and dyno exhaust.

After a 20-minute break-in period, the new CHP/FPS 4.6 was run in anger and tuned to produce 308 hp and 347 lb-ft of torque. This new combination represented a jump in power of 44 hp and 21 lb-ft of torque over the original long-block, through the power difference was as great as 68 hp at 6,000 rpm. Given the minor gains achieved thus far with the project, we were excited to finally see some big numbers appear on the screen. Though we still had not improved the power output enough to reach our goal of 300 hp, we had taken a serious bite out of the required power gain.

Both the intake and exhaust ports received extensive CNC porting to improve the flow potential. According to FPS, the porting increased the intake flow from 162 cfm to 201 cfm.

While we had come up shy after combining the new CHP short-block with the FSP ported heads, we still had at least one ace up our sleeve in the form of more aggressive cam profiles. Until now, both the original 200,000-mile and new CHP/FPS combinations were run using the XE262H cams supplied by Comp Cams. As with all of the non-PI cams, the XE262H cams featured 0.500-inch lift. The smallest of the Xtreme Energy grinds for the early Two-Valve modular motors offered a 224/232 duration split (at 0.050) and a 114-degree lobe separation angle. While we liked the combination of power and driveability offered by the XE262H, we knew there was more power to be had with a larger cam profile.

To that end, we selected the largest of the XE series, the XE274H. These cams offered the same 0.500-inch lift, but increased the duration split from 224/232 to 236/240 degrees. Both cams featured the same 114-degree lobe separation angle. Installation of the larger XE274H cams took less than 1 hour (we've become pretty proficient at cam swaps on the Two-Valve motor), and in no time the mod motor was ready for tuning. Running the same air/fuel and timing (13.0:1 and 30 degrees total), the XE274H cam increased the peak power output to 317 hp and 349 lb-ft of torque.

The new cam profiles offered decent power gains, but we were actually expecting a bit more given the change in duration. At 6,000 rpm, the largest gain was 17 hp, but the all-important peak-to-peak gain was just 9 hp. That extra 9 hp brought us that much closer to achieving our 300hp goal, but it was not without cost-namely, some low-speed torque and, more importantly, driveability. Compared to the smaller XE262H cams, the larger X274H profiles lost power up to 4,100 rpm. Though the losses were never more than 9 lb-ft, the daily driver status of this project car means we will be running the motor where we experienced a power loss much more than where we experienced a power gain.

Before installing the 4.6 back in the awaiting '96 GT, we decided to try one final upgrade. With limited parts available for the early (non-PI) motors, I took it upon myself to design an intake manifold for the early Two-Valve motors. Remember that this intake design was tested in prototype form, and we (the magazine) will reserve judgment until a production version can be properly tested. But the results were pretty impressive-even more so considering the prototype intake was actually designed for the later PI head, thus resulting in a significant port mismatch between the PI and non PI components.

The chambers also received some polishing, not to mention a set of new SI stainless steel valves to further improve the flow.

The mismatch notwithstanding, the intake was secured to the non-PI heads and run in anger on the engine dyno. Equipped with the new intake design, the peak power jumped from 317 hp to a whopping 355 hp at 6,200 rpm. Even more impressive was that the intake design did not lose any power down low (as is often the case). The intake design improved the power output from 2,900 rpm (the lowest test point) through 6,500 rpm, registering gains as high as 50 hp over the stock non-PI intake.

Though the torque gains were most signifi-cant past 4,800 rpm, at 3,800 rpm the intake increased torque production by 24 lb-ft. Look for a production version to appear on the 4.6 for chassis dyno testing as we (hopefully) finalize the quest for 300 hp and can finally step up to forced induction.

We installed the engine back in the car for a shot at the chassis dyno. After installation and tuning, the fresh combo put down 276 hp and 315 lb-ft of torque. Finally, a significant step toward our goal of 300 hp.

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.