Reality Checklist: GT 500 Bolt-Ons

Kevin Booth scored this bad-dude, '07 Shelby GT 500 in an eBay deal withan Illinois Mercedes dealership and saved a ton of cash. Our testvehicle came to us having nothing more than a few suspension modsalready done and low miles on the odometer. That's the way we like 'emfor these kinds of projects--mechanically bone stock.

Horse Sense: Prices are an interesting issue withShelby parts. On one hand, once you look at MSRPs, you realize there arebetter deals on the Internet and through wholesale performance outlets,such as Summit Racing (www.summitracing.com). On the other hand, pricesare irrelevant for those who can afford a GT 500.

Sometimes even we, the staff of 5.0 Mustang & Super Fords, are amazed bythe effect hype has on 'Stang enthusiasts. In a nutshell, it sometimesmakes 'Stangbangers go absolutely nutty. Sure, we do a fair amount ofboasting about cars or parts that truly impress us. When we're reportingon solid-gold winners, and even the one-hit wonders, our main objectiveis to keep the information real and present to you the facts--especiallywhen we experience them firsthand.

Word of Gibson's new X-shape crossover sparked the initial flame forthis tech project. The 21/2-inch, mandrel-bent aluminized steel (alsoavailable in stainless) tubing dramatically increases exhaust flow overthe restrictive factory piece and its catalytic converters.

Hype certainly played a big role in the immediate success of Ford's '07Mustang Shelby GT 500. From the moment 'Stang nuts first heard rumorsthat Ford might build and offer a supercharged S197 to the car'sofficial announcement, production, and eventual rollout in fall 2006,energy for Shelby coupes and convertibles has remained high. While thenear $100,000 markup prices for new Shelbys have come down considerably,the cost of a new GT 500 still ranges between $50,000-$60,000.

The Shelby's Eaton-blown 5.4 engine and its advertised 500 hp sits highon the car's hype ladder. For the enthusiasts lucky enough to own onebut don't really understand the difference between flywheel andrear-wheel performance, boasting about its 500 ponies comes naturally.The pride owners have in their investment is certainly understandable.

Our second phase of product test centers on K&N's new AirCharger CAIsystem for '07 GT 500s. The air-intake kit eliminates the restrictiveflow of the OEM airbox/filter combination. As we saw in our tests, itrams a huge amount of air into a Shelby's supercharged 5.4.

We hard-core 'Stangbangers know that when it comes to claiminghorsepower that's worth bragging about, all bets cancel at the rearwheels--not the flywheel. At this point, it's widely known that the"500" in a Shelby GT's name represents 500 hp. Since the number is oftenmisunderstood as being rear-wheel horses, we thought we'd try to clearthings up by installing and dyno-testing a few Shelby-specific bolt-onsthat should make Ford's super 'Stang live up to its name, and moreimportantly, its lofty power claim.

The parts assortment, installed by Saul "The Surgeon" Gutierrez ofExtreme Automotive in Canoga Park, California, consists of Gibson's newcatless, 21/2-inch X-shape crossover (PN 619008; $226.65/aluminized,$346.65/stainless steel) and exhaust system (PN 619006; $652.35), K&N'sShelby GT 500 AirCharger cold-air intake kit (PN 63-2571; $449.00), anda 2.6-inch supercharger pulley with 90mm tensioner pulley/160-degreethermostat/custom-SCT-tune package (a.k.a. Pulley Pack PN 900045;$599.00) from Paul's High Performance of Jackson, Michigan.

Paul Svnicki of Paul's High Performance offers this 2.6-inch blowerpulley and 90mm tensioner-wheel setup designed specifically for ShelbyGT 500s...

If this parts list seems familiar, it's probably because these are thesame entry-level upgrade parts you've read about in our similar testsfor Fox, SN-95, New Edge, and Three-Valve S197 'Stangs.

Kevin Booth was kind enough to lend us his Shelby 'Stang for a day ofinstallation and dyno evaluation at Extreme. All tests were done withengine temp constant at 170 degrees, but we noticed that the GT 500'siron-blocked engine doesn't dissipate heat well. Since heat rises, theblower remains heat soaked for quite a while after the engine has beenrun hard.

...Paul's upgrade system includes a 160-degree thermostat and acustom, SCT flash tune that optimizes air/fuel accordingly, with regardto increased intake and exhaust airflow, for smooth, low-rpmdriveability.

As usual, our testing is done with California's 91-octane pump gas,which with proper tuning, we feel can be used up to a 550hp limit onShelbys. Naturally, race fuel permits making more power, but keep inmind the connecting rods in Shelby engines aren't forged and are likelythe first parts to go when they're taken to the limit.

As you'll see when you read further, there are individual and collectivemerits for all these simple Shelby bolt-ons, making them smart choicesas first-step upgrades for enthusiasts who like to boast.

CLICK HERE FOR THE DYNO SHEET ON ALL THE PARTS USED IN THIS INSTALL

Here's a comparative look at Gibson's new X-shape crossover (left) andour test Shelby's OEM catalytic crossover tubing. Other than the obviousabsence of cats, the other major differences between the two are the Xintersections on each. While the stock cat pipe's X gives the impressionof gasses meeting in a smash-mouth fashion, Gibson's pipe features aradiused merge, which disperses exhaust smoothly and with much greatervelocity than a stock pipe. Shelby fans need to understand that thiscrossover isn't legal for street use, as it doesn't include catalyticconverters.

Gibson Exhaust

Swapping crossovers and bolting on Gibson Performance's after-catexhaust system is the first leg of our Shelby upgrade journey.

Unlike exhaust on its Fox, SN-95, and New Edge predecessors, there's nocutting necessary when removing exhaust systems on S197 Mustangs, sotaking the tubes off our test car is a quick and easy deal. Installingthe Gibson X-shape crossover is a drama-free experience, and each pieceof the kit's exhaust piping fits without any modifications.

The sound created by a blown 5.4 with no cats is different, and quitefrankly, it takes getting used to. Decibel levels jumpdramatically--both at idle and especially when the hammer is dropped--asthe engine takes on a much louder, deeper, and raspier note. The soundis completely different than the stock exhaust, which seemswhisper-quiet in comparison.

Without tuning, the exhaust swap showed us a nice power bump and anearly identical gain on the torque side. Going catless with a Shelby'sexhaust is a good first move, as it will ultimately benefit from all theengine-performance upgrades an owner will make as time goes on.

The factory exhaust band clamps must be reused on the Gibson pipe, somake sure they aren't discarded after removing them from the stockpiece. Gibson supplies new crush-style clamps for the exhaust pipes andmufflers.

Gibson's free-flow tube features hangers in the factory location and isa direct, bolt-in replacement that doesn't require any abnormal amountof fighting or finagling to hang. Oxygen-sensor bungs are included intheir correct location, so there's no need to extend wires or create newwiring for the sensors. Saul drills the passenger-side tube and welds inan additional bung, which will be used for the dyno's wideband O2sensor.

Using the 'Stang's original rubber hangers, Saul installs the 21/2-inchstainless mufflers included in Gibson's after-cat dual exhaust kit for'05-'07 Mustangs after connecting exhaust pipes from the crossover. Eachmuffler includes a 4-inch intercooled tip and is embossed with theGibson logo across the top and on the bottom of each can.