Michael Galimi
February 1, 2008
Photos By: Craig Berry
Smoking the Nitto 555R tires is easy when you have 731 rwhp and 666 rwtq on tap.

Nearly a year ago, MM&FF took a showroom-stock '06 Saleen Mustang and tossed on a Hellion turbo kit. Emerging from the chassis dyno room at Crazy Horse Racing was a Saleen of a different breed. It was as if our test vehicle turned into a disobedient machine-in a good way. The boost knob was turned to 17 psi, and we watched a completely stock Mustang deliver 570 rwhp. Since that day, the car's owners, Billy and Bryan Sorby, have had a tire-smokin' good time, and let's just say there are some '07 Corvette Z06 owners who are still licking their wounds.

The Saleen we tested is killer in its own right, but we begged the crew at Hellion Power Systems, led by three-time NMRA champion John Urist, for more. He obliged and let us follow along as they took the company's '05 Mustang GT one step further. The Saleen had a stock engine, and we couldn't dare push more boost or install a larger turbo without the fear of blowing the stock short-block to smithereens. The Hellion Stang was to be the recipient of a fortified short-block, enabling us to drop on a larger, more powerful turbocharger.

Utilizing a 76mm turbocharger enabled our test vehicle to register 731 rwhp and 666 rwtq-from a 285ci engine wearing untouched stock heads and factory camshafts.

Our first test with the Saleen utilized a 62mm turbo that was specifically designed for stock and mildly modified engines. Thanks to a fortified bottom end in this installment, Urist opted to go with a 76mm turbo. "We went with the larger turbo because the new engine was capable of handling it," he says. "This head unit is built by Turbonetics, as are all the turbochargers in the Hellion kits."

Upgrading the turbocharger is rather easy with the Hellion kit-the small-frame 76mm housing fits the standard S197 turbo system without any problems. It's a direct bolt-on piece, so you can add one to your kit down the road. We also liked the fact that this system doesn't require any cutting or serious modifications to your car.

The Turbonetics head unit features a 14mm larger inlet, a more efficient exhaust housing to turn the impeller harder, and the same optional ball-bearing setup as the 62mm unit. Utilizing ball bearings on the shafts enables the turbo to spool up quicker. Spooling is the term used for building boost pressure in the manifold. The 62mm base turbo will operate efficiently to approximately 550-600 rwhp. The larger 76mm turbo, on the other hand, has proven to be effective up to 800 rwhp in the proper application.

Here's the Turbonetics HP76 turbo with a F1 S-Trim turbo wheel. Classifying turbos seems to be getting harder these days, as the manufacturers constantly make changes to keep up with the variety of applications on which turbos are used. This head unit is capable of producing in the low 800-rwhp range in certain applications, thanks to its high-pressure turbo wheel.

Our test car spun the chassis dyno to 731 rwhp and 666 rwtq at 20 psi. We grinned with the torque figure; it's quite ironic given the turbo company's hellish theme. The boost peaked at 20 psi, but the average boost number was 18 psi. Urist explained more on the boost numbers, saying, "The 62mm is efficient to about 15 psi. The 76mm turbo has a high-pressure wheel and is way better and efficient at higher boost levels than the standard 62mm."

The 731 was an impressive number, but it wasn't nearly as much power as the '03-'04 Cobra 76mm kits from Hellion that we tested a few years ago. Urist credits that to the fact the Cobra engine has a better set of cylinder heads. "The Four-Valve heads are more efficient," he says. "The combustion chamber is much better than the Three-Valve chamber. You can't get away with pump gas as easily with the Three-Valve engines as you can with the Four-Valve." We were still impressed with the fact that this Mustang made 731 rwhp relatively effortlessly.

The stock modular block was used for this buildup. The bores were enlarged 0.030 inch more than stock.

Kuntz and Company was tapped to build the short-block. The company is probably best known for being a longtime race-engine shop out of Arkadelphia, Arkansas. This modular engine build was to let the world know Kuntz and Company isn't just a high-end race-engine shop, but also a place that does stout street engines. The stock-block's bores were enlarged by 0.030 inch, and the holes were filled with off-the-shelf Arias pistons and Eagle rods. The piston-rod combo swings off a stock-stroke steel crankshaft. Compression ratio sits at a turbo-friendly 8.5:1. The bottom end was designed to withstand the rigors of boost, no matter what the Hellion crew cooks up for this R&D car.

Topping the modular short-block are stock heads and camshafts. Urist wanted to push the factory pieces to the limit and felt the stock castings flowed enough air to support the volume of boost the turbo was capable of injecting into the engine. "Turbos are less affected by heads and/or camshaft changes when compared to a naturally aspirated or supercharged engine,"he says. "With this in mind, there are minimal gains from headwork and camshafts with this combination. I suggest saving time and money and invest it in fortifying the rest of the engine." That's not to say you won't pick up power with that work, just not enough to warrant spending another grand or two. The money saved could be better put in other areas of your S197 Mustang, such as the fuel system and drivetrain.

Just having a strong engine to survive 20 psi of boost isn't enough to go out and trounce the dyno rollers. Other pieces of the puzzle included a Modular Mustang Racing (MMR) complete fuel system, consisting of a -8 feed line with a billet Y-block, fuel filter, and billet MMR fuel rails. They deliver the fuel to eight 60-pound injectors. Nate Phillips used DiabloSport software to tune the stock computer. Backing the potent turbo engine is an ACT single disc clutch, much like the one Urist employed behind the twin-turbo '03 Cobra we covered in the Jan. '08 issue ("The Manhattan Project").

Break-in consisted of roughly 500 miles that Hellion's Dwayne James happily drove. He cruised the streets of Albuquerque, New Mexico, and resisted the temptation to mash the throttle. A quick oil change and the car was strapped to Dyno Edge's DynoJet chassis dyno. A few easy pulls were made to check the air/fuel ratio, and then the staff let it rip. A mere 17 degrees of timing were dialed in, and the Three-Valve engine sucked in Trick 101 fuel. We watched patiently as the car threw up power in the 650-rwhp range. Phillips played with the computer and made some more pulls. Power shot up to the 680 range. He then did a few tricks with the variable camshaft timing. We saw huge gains with the changes. The final results were an outstanding 731 rwhp and 666 rwtq.

The Hellion '05 Stang exhibits docile street manners and a stock idle, thanks to the stock camshafts. That story changes when the hammer is dropped. A chain is only as strong as its weakest link-having a fortified bottom end ensures this chain won't break when it drags LS-powered cars down the strip.