KJ Jones Senior Technical Editor
December 1, 2008
Photos By: KJ Jones

Horse Sense:
The word simple is one of the most relative terms a magazine editor can use when describing the installation of parts for late-model Mustangs. Yes, there are often occasions when mags are stone-cold guilty of calling an install simple, without taking into account the fact that a project's degree of difficulty may actually depend on the skill and ability of the person doing the work. Rest assured, we try to weigh all the variables associated with putting parts on Mustangs before we start talking about how simple it is. What might be easy for one enthusiast could be a nightmare for another.

Testing and reviewing the latest technology for Mustangs makes up a large part of the work we do, so we constantly try to think of new ways to put parts, especially high-performance parts, for Fox, SN-95/New Edge and now S197 'Stangs, through the proverbial "wringer" to tell you all about how they perform.

When we discuss 5.0 and 4.6 engine upgrades, we're also mindful of the cost for parts being used-individually or as a system or package-the ease or degree of difficulty for the modification, and the end result, more commonly known as the difference in rear-wheel horsepower and torque that the change or changes make.

While we work hard to maintain some sense of balance in the way we cover the different Mustang platforms from a tech perspective, our editor, Steve Turner, recently acquired an '08 Shelby GT500, which has definitely increased the interest for exploring different methods of modifying the special-edition, factory-supercharged Ponies. Steve's car, also known as Project Vapor Trail (for its Vapor Silver finish), is our in-house GT500 lab rat, of sorts. As we hope you've noticed, Steve has joined the steadily growing crowd of Shelby owners that get props from us for digging right in and making improvements to their cars-in some cases, before they even get them home. Case in point: Steve added the all-new Ford Racing Performance Parts' Shelby GT500 upgrade supercharger-the blower is covered by Ford's warranty, since it was installed by Anderson Ford-and a beyond-bitchin' Glassback roof from CDC ("Fortunate Sun," Oct. '08, p. 128) right away. In the wake of those improvements, our leader also added underhood aluminum dress-up pieces from Moroso (detailed in Steve's blog on our website), as well as VMP Tuning's trick, boost-building, 2.65-inch Stock-Look blower pulley. The car also has a custom tune, made with SCT tuning gear while the GT500 was strapped to a chassis dyno at VMP's headquarters in Debary, Florida ("The Invisible," Nov. '08, p. 96).

The bone-stock, supercharged 5.4 in Carlos Cortez's Shelby GT500 didn't have the steam we thought it should, but the situation wasn't anything that a few good bolt-on parts couldn't fix. Yes, we're jaded.

Yes, in only two short years, the full-on, bolt-on phenomenon has made its way to Shelby GT500s, too. And similar to the '03-'04 Cobras, there's one particular group of pieces-a cold-air intake system, a smaller blower pulley, free-flowing mufflers, a larger heat exchanger, and PCM modifications using a hand-held tuning device-that really seem to do wonders for the Shelbys when they're in bone-stock trim. It's become a budget-friendly mainstay for the factory-boosted S197s.

Thanks to Editor Turner's vested interest in all things Shelby GT500, we've decided to install the top five entry-level bolt-ons, selected by Steve, and give you the low-down about their effect on the receipient, a 1,700-mile '08 stocker owned by Carlos Cortez.

As the owner of SI Valves of Simi Valley, California, the company that set us up with new Competition Series stainless-steel intake and exhaust valves for our T-top coupe's damaged cylinder head last year, Carlos is a performance-minded enthusiast. His "just-let-me-know-what-day-you-need-it" response when we asked to use his new ride for a tech project confirms that Carlos is a card-carrying member of the Ain't-Scared Club-a rapidly growing secret society of Shelby GT500 owners who clearly have no interest in keeping their 'Stangs totally stock for the length of the factory warranty period.

The boss chose parts from Bassani, DiabloSport, Fluidyne, JLT, and Steeda for this tech effort. You may recall our previous report on a similar evaluation of GT500 bolt-ons from Gibson, K&N, Metco, Paul's High Performance, and SCT. Check out those performance results in the archive of tech articles on our website (www.50mustangandsuperfords.com).

The Fluidyne coolant-pump bracket (PN FHP-07GT500KIT; $49.99) bolts directly onto the heat exchanger assembly and allows us to keep the stock pump in place for coolant circulation through the unit.

The information in this article is presented in the same format we used to detail the bolt-ons in "Reality Checklist" (Apr. '08, p. 124). Each capsule includes part info and highlights its installation. This time, however, we're waiting until the end of our report to let you know the collective impact our upgrades had on a stock Shelby GT500's rear-wheel performance.

Before going any further, note that Horse Sense for this story discusses use of the term simple in magazine tech articles. With the exception of the tuning work that is done using the chassis dyno, there honestly isn't anything overwhelmingly difficult about bolting any of the pieces we're using on a Shelby. Sure, having a twin-post hoist and/or the mechanical skill and knowledge of someone like Extreme Automotive's Saul "The Surgeon" Gutierrez would be nice. But what makes this group cool is that the parts can be installed by mechanically inclined do-it-yourselfers, those who are only able to elevate a Mustang as high as a good set of jackstands allow.

As you'll see when you read on, nothing in this group of parts requires additional fabrication or modifying for installation, and it's possible to have everything installed and your Shelby back on the road in 4 to 6 hours if you're doing it yourself.

Keep in mind that maintaining an air/fuel ratio below 11.8:1 at wide-open throttle is critical for supercharged Mustangs such as Shelby GT500s. All the timing and fuel adjustments for this particular setup can be made using the DiabloSport Predator's preloaded JLT CAI/2.7-inch pulley tune and the Shelby-specific unit's provisions for timing and fuel adjustments. However, using a wide-band air/fuel gauge is strongly recommended if you elect to tune it this way instead of on a chassis dyno.

This replacement requires breaking the bumper assembly down to its core. Using 13mm sockets and wrenches, Saul removes the inner bumper, which allows him to fully dislodge the stock heat exchanger from the bumper. Upper and lower hoses are disconnected at this time. Make sure a catch can or bucket is in position before disconnecting any of the lines. This helps prevent having to clean up a river of coolant when the exchanger is pulled.

Fluidyne Heat Exchanger
Despite its intercooler and small heat exchanger, one of the big problems with a Shelby's stock blower is that it heat-soaks in a hurry, which leads the PCM to pull timing, making power the victim. To remedy this, especially when making mods for increased horsepower, adding a large-capacity heat exchanger is a good idea.

We're treating Carlos' GT500 to Fluidyne's low-temperature radiator unit for Shelby GT500s (PN FHP30-05MUSLTR; $499.95). The new exchanger is twice the size of the OEM Shelby GT500 unit, thus helping to increase both the blower, and especially the intercooler, efficiency quite a bit. Installing the heat exchanger is the most time-consuming task out of all the upgrades we make. If you're doing this job yourself, allow about an hour to remove and replace all the pieces (that's if you're really going for it).

JLT Cold-Air Intake
JLT Performance's cold-air intake system (PN CAI-GT500-0708; $449) definitely has all bases covered when it comes to looks and functionality. Thanks to its super-trick, carbon-fiber intake tube, JLT's kit is 2 pounds lighter then a Shelby's OEM intake tube and airbox. The system also features an enormous, 110mm mass air housing (the factory sensor is retained) and includes all the pieces required for an easy installation, which shouldn't take more than an hour.

Steeda Supercharger Pulley
Installing Steeda's 2.7-inch Shelby GT500 supercharger pulley (PN 555-3345; $159.95) is another "quickie" component in the upgrade package we're installing on Carlos' ride. Saul has the stocker off and the new smaller-diameter pulley in place in about 45 minutes. A smaller pulley increases a blower's speed, which in turn raises the amount of boost the supercharger generates.

Bassani Aft-Cat Exhaust
Bassani's 21/2-inch, stainless steel Aft-Cat exhaust system (PN 4607SR5; $498.39) rounds out the hard parts we installed on Carlos' Shelby. Similar to the other installation tasks that were performed, there really isn't anything exotic about the swap procedure. As long as you're able to raise the car high enough to work under it without too much hassle, this leg of the project is a 30-minute deal.

The JLT setup is sano. The carbon-fiber intake tube looks great and the system is clearly designed to ensure direct, smooth airflow into the throttle body.

DiabloSport Predator
With all the changes we've made to our project Shelby, there's no doubt the air/fuel mixture is now much leaner than it was when the car was in stock trim. We're using DiabloSport's Predator unit for Shelby GT500s (PN U7145; $369.99) to make things right with the PCM's calibration and ensure that Carlos' ride runs smoothly, and warning lights aren't triggered. The Predator contains a series of GT500-specific tunes that modify spark and fuel functions associated with the type of bolt-on upgrades that are made.

Saul selected Predator's JLT cold-air intake/2.7-inch pulley (with 93-octane fuel). With the exception of our project being limited to 91-octane gas, the tune proved to be just about spot-on. It only required a small amount of fine adjustment, which Saul was able to adjust directly with the Predator. Since we're using the dyno to measure performance, a wideband O2 sensor helped us determine the correct amount of fuel to add to the tune, which ended up being a total of 5 percent from 2,000-7,000 wide-open throttle, bringing air/fuel down to a more-than-safe 11.0 across the rpm range. Had we added a complete, 3-inch exhaust system on Carlos' car, a more detailed dyno tune using DiabloSport's Chipmaster Revolution tuning software would be necessary.

Carlos' Shelby gave us quite a surprise during our initial test for baseline horsepower and torque data. Based on the performance of other stock Shelbys that we've tested on Extreme Automotive's Dynapack Evolution 4000 chassis dyno, we expected to see peak horsepower in the neighborhood of 442-446 at the rear wheels. Our test subject fell way short of that benchmark, recording a somewhat-disappointing 426.41 peak rear-wheel horsepower and 372.08 lb-ft of torque.

Call it a "wall of silence," if you will. This blockage inside a Shelby's stock mufflers is not only detrimental to how the car sounds, it also hinders performance in a big way.

The jury is still out on why the numbers were so much lower, but one variable that may have had some influence in the car's performance (before and after the upgrades) is the ambient temperature inside the dyno cell. Unfortunately, we can't always perform dyno tests or other critical evaluations during "perfect" weather conditions. With a June heat wave gripping the San Fernando Valley and highs reaching upward of 111 degrees in Canoga Park, where Extreme is located, our Shelby project was done in 107-degree heat. So hot weather might have had something to do with it. However, we're not saying that ambient temp alone sapped approximately 20 hp from Carlos' car in stock trim, and we're not saying the car had some sort of mechanical or drivetrain problem. The bottom line is that the dyno doesn't lie, and it is what it is.

In that vein, the parts we put on Carlos' GT500 definitely are what they are-power producers. In just over half a day, we bolted on (and plugged in) a total of five simple performance parts that added more than 127 peak horses at the back tires at 6,000 rpm.-an incredible gain considering the relatively low cost for everything, and the money saved on labor if you install the parts yourself.