Dale Amy
September 27, 2010
Photos By: E. John Thawley, III

James Davenport is in the shipping and delivery business, where speed is of the essence. His philosophy of velocity obviously extends to his '06 Saleen S281. Problem was, even in the first year of ownership, the Saleen's boosted, 435hp 4.6-liter Three-Valve just wasn't enough for the California businessman. His horsepower jones soon had him rolling east to the Arizona facilities of AMP Performance for a fix.

In Phoenix, AMP's Chris Ciolek took on the task of ramping up the screw-blown S281's thrust, and began with some cost-effective prescriptions like a pulley swap, cold-air kit, custom tune, and other tried-and-true bolts-ons. These mods conspired to push rear-wheel horsepower over the 500 mark. But that still fell short of Mr. Davenport's desires, and a decision was made to go after some more displacement. An interesting sidebar here is that the discussions now centered on not just the Davenport Saleen, but also another one-identical except for color-belonging to his business partner. It was ultimately decided that both cars would receive identical new 5.4-liter transplants that would get their boost from turbocharging.

Bear in mind that this was back in 2006, well prior to the introduction of the Shelby GT500, so the displacement solution wouldn't be as simple as bolting in complete Snake powerplants. Instead, Chris was faced with a build-your-own situation, and so ordered a pair of 5.4-liter F-150 Lightning blocks (which he says share part numbers with the later GT500 casting) and used them and their cranks as the foundation for the parallel projects. Other bottom-end hardware on the build list included Oliver billet rods and JE pistons dished for about 8.5:1 compression.

Likewise, GT500 heads weren't yet on the market, leading Chris to opt for available Terminator Four-Valve castings and order some custom-ground cams, along with cast intakes from Sullivan that were compatible with the Terminator port configuration. Once assembly was complete, the next big chore was to adapt Hellion's S197 GT turbo kit, replete with a T-76 Turbonetics upgrade, to engine bays now stuffed with 5.4 liters and fat Four-Valve heads. Needless to say, a little fabrication by the AMP crew was involved. When all was said and done, that setup yielded 740 rwhp at around 24 psi. However, Jim Davenport seemed to have his heart set on something north of 800. And the customer is always right ...

On one dyno pull, an oil pump broke; this provided an opportunity to swap on some stock Terminator Cobra cams in place of the lumpier custom sticks. According to Chris, these stock cams made all the difference in the world insofar as adding scads of low- and mid-range power. More mid- and top-end gains came from the substitution of a Hogan's sheetmetal intake. And in one more mod, a billet-impeller 76mm Precision turbo was worked into the system. In this particular combination, that turbo's billet impeller proved "leaps and bounds" better, according to Chris.

The end result is 830 rwhp at 17 psi-a power level at which the 65-lb/hr injectors are pretty much maxed out. We're told that this output was recorded on a Fifth-gear dyno pull, as all attempts in 1:1 Fourth gear resulted in massive tire slippage. The AMP crew suggest that a successful Fourth-gear pull would have registered about "12 to 15 percent" more power. Still, we could live with 830 ponies ...

By now you've likely noticed the pair nitrous of bottles in the trunk (on either side of the additional 15-gallon fuel cell and in front of the ICE gear). Though it does add peak power, the Speedtech nitrous system is currently utilized primarily in the lower rev ranges before the turbo gets well and truly spooled up. So the juice, in this case, is more for hair-trigger throttle response than outright power.

As you might imagine, this was a labor-intensive six-month project on AMP's part-or projects, since the result was two mechanically identical mega-power Saleens-but you can see from our engine shots that popping the hood is guaranteed to suck the eyeballs right out of the heads of any nearby spectators. Come to think of it, popping the trunk is likely to have the same reaction.

Such a project would be far easier today, of course, what with the ready availability of complete GT500 long-blocks with their plug-and-play intercooled lower intakes. But sometimes it's worth a little extra effort just to get there first. Just like in the shipping business. Right, James?

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