Car Feature: Kenny Brown's GT500-RS 001

Photos by: Editor Mark Gearhart

What happens when you put a GT500 in the hands of one of the country’s most capable Mustang tuners? You get the Kenny Brown Performance GT500-RS, a GT500, with the full KB GT4-RS treatment. The GT4-RS package from KB can turn any late model Mustang into a track day, super car slayer. Throw in the power of the GT500, and the car becomes the ultimate track day weapon, easily capable of out handling vehicles that cost two to three times as much at the track.

This particular GT500 belongs to Phillip Meyer from Texas. Meyer hangs out with several other Shelby owners in his area, “He basically wanted a car that will spank the other guys on the track,” said Kenny Brown. Meyer had already upped the performance of his GT500 to 750 hp with a Kenne Bell 3.6L supercharger, and now it was time now to solidify the handling. So he shipped the car to Kenny Brown Performance near Chicago, IL for the full GT4-RS treatment…plus some extras.

With 750 HP already on tap, Meyer wanted his GT500 to have handling capability that matched the car's horsepower.

The GT4-RS Package

He basically wanted a car that will spank the other guys on the track – Kenny Brown

Kenny Brown has been developing suspension packages for Mustangs for over 30 years, and at his own company (Kenny Brown Performance) for over 25 years. In recent years Brown and his team have developed several different suspension and performance packages for late-model Mustangs. The GT4 line comes in various levels ranging from a street going package that will give any new Boss 302 a run for the money, to full on competition ready track machines. Customers provide the car, and the team at KB transform it into a handling beast based on the chosen package, customer’s desires, and planned usage of the car.

The GT4-RS package is KB’s top of the line setup for street and track day Mustangs. “This customer wanted the full GT4-RS package, plus some other stuff” says Brown. The standard GT4-RS package normally includes a drool inducing list of upgrades.

Long tube headers along with a Kenny Brown Performance K-member and control arms are just part of the upgrades.

Engine

As part of the GT4-RS package, the radiator is also swapped for a heavy duty unit, with positive flow ducting to better direct air flow. All GT4-RS cars also receive a road race oil pan. Producing 750 hp Meyer’s GT500 exhales through a set of long tube headers, off-road X-pipe, and three inch high flow race mufflers. In addition to the standard GT4-RS package, and what Meyer had already done, the team at KB performed some more modifications. The engine was lowered to improve center of gravity. The engine oil cooler was swapped out for a double pass Porsche style unit. The supercharger heat exchanger was also moved to allow for increased air flow across it.

Track Ready Rear Axle

With the GT500 already having a TR6060 transmission on board, the KB crew turned their attention to the rear axle. Leaving the final drive ratio at 3.31:1, a KB-spec torque sensing differential was installed, along with a Boss aluminum rear differential cover. The piece de resistance in the drivetrain though is the customer requested Baer floater rear axle conversion; this modification is not part of the normal GT4-RS package.

It alleviates stress on the rear axle shafts by converting the rear axle to a full floater system, complete with hubs, and axles splined on each end, similar in principle to what is used on many heavy duty trucks. The installation of the full floater kit requires a skilled fabricator with the proper tools and experience. When completed properly it gives the car more predictable brake performance, improved handling, and better axle shaft and axle bearing life.

From underneath the car the evidence of modification becomes more clear. What is not fully understood even from this angle is the extensive work to the rear axle to convert it to a full floater setup. The Baer floater conversion helps eliminate pad knock back under braking.

Chassis

Of course all that horsepower is meaningless without a proper chassis. That is where KB’s years of experience with Mustangs of both the street and race variety really shines. The parts lists for the GT4-RS chassis, consists of virtually everything you can order from the company for a late-model Mustang, all installed by the pros who designed the parts. There are of course the KB Jacking Rails, as well as their Matrix Chassis Support System, both are KB chassis staples that we’ve seen on Mustangs since the Fox Body era.

All GT4-RS cars get the complete Advanced Geometry Suspension system (AGS 4.0) for the ultimate handling experience. There’s an adjustable front sway bar, KB selected Eibach 2.5-inch springs, as well as JRZ KB Spec single adjustable coil overs. Up front you’ll also find a KB lightweight K-member replacing the factory stamped steel piece, as well as the company’s front control arms. In the rear there’s a full set of adjustable control arms as well as an adjustable panhard bar. The car’s ride height is adjustable, and steering is improved by way of the use of a Boss S electronic power steering unit. An upgrade to ARP long wheel studs provide additional safety.

Fast and Slippery

Standard on the GT4-RS are a number of appearance and aerodynamic upgrades. Cheating the wind are a set of functional exterior modifications designed to improve down force and air flow around the car. The GT4-RS package includes a set of side skirt splitters, a PBR Sport Plus rear wing, and a custom front spitter with fender air dams. KB also installs their signature custom graphics.

Helping those aero changes keep the car glued to the track is a set of KB spec Forgeline Monoblock GA1R wheels, also part of the GT4-RS package. Measuring a massive 19×10 inches front and 19×11 inches rear, they are shod in sticky 295/30 and 305/30, Pirelli PZero Corsa Extreme performance tires.

Functional changes like the PBR rear wing, and the KB spec splitters and air dams will help cheat the wind when necessary and harness it for down-force at speed. The appearance package graphics let everyone know this car is the real deal.

Binding Force

Of course no track day upgrade would be complete without the appropriate brake upgrades. The GT4-RS package has this area covered with a KB spec brake system from Baer. The brake system uses Baer’s forged monoblock 6 piston calipers both front and rear, coupled with stainless steel brake lines. Brake rotors are extra large pizza sized at 14×1.25 inches all around. Brake fluid is also upgraded for higher temperatures, and functional front brake cooling ducts are installed from the front fascia to the spindles.

Baer 6 piston calipers and 14 inch rotors provide the stopping power. Massive Forgeline GA1R wheels are built to KB specs, and are both lightweight and strong.

A Boss S ABS module replaces the stock unit. This provides better ABS performance for a track oriented car, and ensures that the safety nannies don’t kick in prematurely and ruin what could be a personal best lap time.

Interior

This car is going to be absolutely awesome out on the track – Kenny Brown

Inside a driver’s left food dead pedal has been added. Special KB plaques are also installed inside the cabin and under the hood. KB also sets up the vehicle log book, history, and maintenance so that the owner can keep track of everything for both personal, and competition purposes.

Brown drove the car both before and after it’s GT4-RS transformation he told us, “Even here in the cold weather you notice that the car has better grip and cornering after we got done with it.” The car is now being shipped back to Meyer. He plans to install a roll bar for competition purposes, and then hit the track for the payoff on the recent upgrades. “This car is going to be absolutely awesome out on the track,” said Brown.

Brown and his team have poured their years of experience into the GT4 packages. If you see any GT4 equipped Mustang in your mirror at the track, chances are you’d better move over, because these cars pack both the horsepower to overtake you on the straight away, and the grip to out maneuver the competition through the corners.

Specs

Engine