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Two Valve Supercharger - Two-Valve Terror
How to keep up by making 700-plus horsepower with 281 inches, two valves per cylinder.
The question is a simple one--is the 4.6L Two-Valve still a player? As if Two-Valve owners don't have enough to worry about with the 300hp Three- and Four-Valve engines, Ford's new 5.0L Coyote upped the power ante by over 100 hp, pushing the Two-Valve even further down the performance totem pole. Now throw in the 400-plus-horsepower 6.2L and 6.4L engines from Chevy and Dodge, and you start to see the uphill battle faced by '96-'04 GT owners.
So, in a world of extra displacement, additional valves, and variable cam timing, can the original 4.6L Two-Valve still compete? The answer is yes, and while it would be difficult to build a naturally aspirated version to run with a new Camaro, Challenger, or Coyote, Two-Valve owners can go wild and wooly with boost.
Kenne Bell recently introduced a new Mammoth kit. The new system includes an oversized air filter, MAF, air intake tube, oval throttle body, Mammoth intake manifold, and your choice of a 2.6L or 2.8L supercharger. Even the lower intake that incorporated a dedicated air-to-water intercooler system was revised, meaning the blower and inlet system cannot be retrofitted to existing kits.
Given the fact that the 2.8L supercharger is capable of supporting over 1,000 hp on the right application, this new Mammoth system is capable of pushing power into the realm of the absurd. Kenne Bell has finally given Two-Valve owners the potential enjoyed by Four-Valve owners.
Big blowers are all well and good, but tremendous power comes from a combination of three things: the engine, the blower, and the induction system. Kenne Bell came through on its end, but a snafu on our end meant we didn't have quite enough engine to thoroughly test the new Mammoth system.
Our plan was to secure and/or assemble a suitable test engine capable of properly testing the merits of the new kit. Scheduling finally forced us to run what we had available, meaning a low-compression 4.6L short-block originally supplied by Sean Hyland Motorsports. The test mule was some six years old, had seen more than its fair share of abuse, and lacked a few components we desired for this test. First and foremost was the compression. We liked the fact that the short-block featured Scat rods and forged Wiseco pistons, but the dish design combined with the 44cc combustion chambers meant we were starting with a compression ratio below 9.0:1.
Our other concern was that the short-block was equipped with a cast (six-bolt) crank, which might become a problem on this high-boost application. Ideally we wanted a 5.0L stroker with a compression ratio over 10:1 to maximize naturally aspirated power before running the blower. In retrospect, wilder cam timing was also required--but enough whining. Let's bring on the boost!
We did have a great set of cylinder heads from Trick Flow Specialties. The Twisted Wedge Race 195 heads featured full porting and CNC chambers along with a 1.90/1.470 valve combination. These are by far the best heads available for the Two-Valve engine. The heads were teamed with a set of XE270AH cams from Comp Cams and run with both the stock PI intake and the Street Burner intake from Trick Flow Specialties prior to the installation of the new Kenne Bell Mammoth supercharger assembly.
After installation of the TFS heads and Comp cams, the naturally aspirated engine was run on the engine dyno using a Fast XFI/XIM management system, Kook's long-tube headers and a Meziere electric water pump. Equipped with the stock PI intake and Accufab throttle body, the low-compression 4.6L produced 348 hp and 349 lb-ft of torque. Stepping up to the TFS Street Burner intake and 75mm Accufab throttle body bumped output to 371 hp and 331 lb-ft of torque. The TFS intake offered as much as 45 hp at 6,500 rpm, but lost out to the long-runner PI intake below 5,300 rpm.