2007 Ford Shelby Cobra GT500
Retro on fast forward. Very fast.
BY TONY SWAN
PHOTOGRAPHY BY AARON KILEY
They say those who fail to learn from history are doomed to repeat it, but Ford's Special Vehicle Team has very carefully studied the Mustang's history—specifically, the chapter on the 1967-70 Mustang Shelby GT500—and is gleefully set to repeat it, in spades, with no less an authority than Carroll Shelby himself adding his blessing and the use of his name. And when it comes to Mustangs, who in today's car biz has more historical cachet? It was Shelby who raised the image of the original Mustang from an engaging all-American sporty car to a turnkey factory racer with the 1965 GT350 fastback. Then he followed up with the GT500, propelled by a big-block (7.0 liter) Ford 428 V-8 generating enough torque (420 pound-feet at 3200 rpm) to pull the skin of the earth measurably tighter when the driver tramped on the gas.
Fast forward to now, and at a glance Ford is reviving that same formula: a stronger engine in a Mustang fastback, delivering more power, more torque, better handling, and more visual intimidation. A little bit of history repeating, right? Well, yes. But that's at a glance. Technology hasn't exactly stood still since the last GT500 rolled out of a showroom in 1970 (see sidebar), and even though this revival preserves a good old live-axle rear suspension—a mechanical tradition that has all but disappeared in current passenger cars—its mechanical credentials are fully contemporary. Not to mention seriously potent.
We brought you a preview of this new super-'Stang in May, a quick thumbnail of the red prototype that was one of the stars of this year's New York auto show. And having sat in and lusted after that show car, we immediately began pestering the Special Vehicle Team development crew, led by Hau Thai-Tang and chief vehicle engineer Jay O'Connell, for an early drive in one of the development cars.
That led to a rendezvous at Ford's proving ground in Romeo, Michigan, on a day in late April that ranged from damp to deluge. Not the right setting for getting acquainted with a muscle car on summer tires, but when you're signed up for an exclusive first drive in the hottest production Mustang ever, you don't quibble.
So what should you expect when this car rolls into showrooms next June?
Certainly, some traits are predictable. Tops on that list is hustle. With output of its supercharged engine forecast by the development team to be "over 450 horsepower and 450 pound-feet of torque," the GT500 will be one quick pony. O'Connell predicts 0-to-60-mph times in the low-four-second range. Similarly, it's not too surprising that this car responds to steering inputs a wink quicker than the Mustang GT and delivers considerably more grip and major-league stopping power.
What is surprising is the level of civility that goes with all of this. The GT500 is by definition a muscle car, but it's not one of those remorseless brass bushing brutes that make their owners pay for visceral gratification with a relentless assault on their hearing and skeletal integrity. The 2001 SVT Mustang Cobra R comes to mind. In contrast, the GT500 should deliver enough compliance to make everyday driving a pleasure rather than a punishment, and we anticipate that interior noise levels may actually be lower than they are in a stock Mustang GT coupe.
Let's talk power. The heart of the GT500 is a supercharged 5.4-liter DOHC 32-valve V-8. If those specs sound familiar, it's because they're interchangeable with the description for the mid-engined Ford GT. But there are important distinctions. The GT V-8 is all aluminum with a dry-sump lubrication system, whereas the GT500 has an iron block and a wet sump. The GT engine is force-fed by a Lysholm screw-type supercharger; the GT500 will use an Eaton R122 Roots-type blower and an air-to-liquid intercooler, adding 10 psi to the intake system at peak boost.
O'Connell says the switch was dictated by availability, rather than price.
"The Lysholm unit is a little more expensive," he says, "but the big problem was supply. They can't make as many as we're going to need. There are performance differences, too. The Lysholm type gives you a little more top end, and the Roots type is a little fatter in the midrange. We think owners will be satisfied with this setup."
Judging by our weather-limited experience at Romeo and our test-track results with the 2003 SVT Mustang Cobra [C/D, June 2002], we concur. Power will be abundant, although O'Connell and his crew were still being cagey about specifics. Pressed on this issue, O'Connell said "between 450 and 500 horsepower—how's that?" Our tech staff warmed up the calculators and figured a forecast of 475 horsepower at 6000 rpm. We may be low.
Big power isn't much good unless it gets to the ground without excessive wheelspin, which is why the production GT500 will have a lot more rear tire than the New York show car, which hunkered over a set of 19-inch wheels wearing 255/45 tires. The initial production run of GT500s will roll on 9.5-by-18-inch wheels with sticky Goodyear Eagle F1 Supercar tires—255/45 front, 285/40 rear.
"We just couldn't get the 255s to hook up," says O'Connell. "Almost every run was going up in smoke."
A pronounced forward weight bias—about 57/43, according to O'Connell—didn't help, either. Part of this is due to increased mass. The supercharged iron-block 5.4 weighs about 175 more pounds than the naturally aspirated 4.6 SOHC 24-valve aluminum V-8 in the Mustang GT. That factor, plus a bigger front-brake package, bigger wheels and tires, and other GT500 package elements, add up to a curb weight projected in the 3850-pound range versus 3575 pounds for the last Mustang GT we tested.
But with the fatter Goodyears managing power delivered by a Tremec six-speed manual transmission and limited-slip rear end, O'Connell is confident the GT500 will sprint to 60 mph in "less than 4.5 seconds," even with its tallish 3.31:1 rear-axle ratio. We expect that when we put the spurs to a test car early next year, a 0-to-60 number will come up in four seconds flat, and the quarter-mile will be 12.5 seconds at 116 mph. For perspective, those runs would be representative times for a C6 Corvette.
Other predictions: O'Connell forecasts a skidpad number of "0.91 or 0.92 g." We think that's a little conservative. Our last two C6 Corvette coupes [C/D, September and December 2004] produced identical 0.98 skidpad numbers. The GT500 will weigh in considerably higher, but it matches the Vette's rear rubber and has even more contact patch up front. Accordingly, we expect to see at least 0.94 g.
Braking: The GT500's 18-inch wheels will shelter huge 14.0-inch vented front rotors with four-piston calipers applying squeeze and 11.8-inch vented rear rotors. (The Mustang GT has 12.4-inch front rotors and 11.8-inch rears, all vented.) Given its Brembo braking system, bigger footprints, and stickier tires, we expect stops from 70 mph in less than 170 feet, which is, once again, Corvette territory. The front rotors on the GT500 show car were cross-drilled and vented. The production car's brakes will lack cross drilling, which looks sexy but tends to produce cracks in hard use.
Handling: The GT500 has hefty front and rear anti-roll bars—a tubular 1.4-inch bar up front and a solid 0.9-inch rear bar—and the spring rates and damping profiles have been adjusted to complement the massive power. There's more roll stiffness, but it's remarkable how supple the suspension manages to be, particularly with a live axle at the rear.
2007 FORD SHELBY COBRA GT500
Vehicle type: front-engine, rear-wheel-drive, 4-passenger, 2-door coupe
Estimated base price: $39,000
Major standard accessories: power windows, driver seat, and locks; remote locking; A/C; cruise control; tilting steering wheel; rear defroster
Sound system: Shaker 500 AM-FM radio/CD changer, 8 speakers
Type: supercharged and intercooled V-8, iron block and aluminum heads
Bore x stroke: 3.55 x 4.17 in, 90.2 x 105.8mm
Displacement: 330 cu in, 5409cc
Compression ratio: 8.4:1
Fuel-delivery system: port injection Supercharger Eaton R122, Roots type
Maximum boost pressure: 10.0 psi
Valve gear: chain-driven double overhead cams, 4 valves per cylinder, hydraulic lifters
Power (C/D est): 475 bhp @ 6000 rpm
Torque (C/D est): 450 lb-ft @ 3750 rpm
Redline: 6000 rpm
Transmission: 6-speed manual
Final-drive ratio: 3.31:1, limited slip
Wheelbase: 107.1 in
Track, front/rear: 61.9/62.5 in
Length/width/height: 188.0/73.9/55.7 in
Ground clearance: 5.7 in
Curb weight: 3850 lb
Weight distribution, F/R: 57/43%
Curb weight per horsepower: 8.1 lb
Fuel capacity: 16.0 gal
Type: unit construction
Body material: welded steel and aluminum stampings
SAE volume, front seat: 53 cu ft
rear seat: 30 cu ft
luggage: 13 cu ft
Front-seat adjustments: fore-and-aft, seatback angle; driver only: front height, rear height, lumbar support
Restraint systems, front: manual 3-point belts, driver and passenger front and side airbags
rear: manual 3-point belts
Front: ind, strut located by a control arm, coil springs, anti-roll bar
Rear: rigid axle located by 2 lower trailing links, 1 upper;trailing link, and a Panhard rod; coil springs; anti-roll bar
Type: rack-and-pinion with hydraulic power assist
Steering ratio: 15.7:1
Turns lock-to-lock: 2.6
Turning circle curb-to-curb: 39.0 ft
Type: hydraulic with vacuum power assist and anti-lock control
Front: 14.0 x 1.3-in vented disc
Rear: 11.8 x 0.8-in vented disc
WHEELS AND TIRES
Wheel size/type: 9.5 x 18 in/cast aluminum
Tires: Goodyear Eagle F1 Supercar; F: 255/45R-18, R: 285/40R-18
PERFORMANCE (C/D est)
Zero to 60 mph: 4.0 sec
Standing 1/4-mile: 12.5 sec @ 116 mph
Top speed (governor limited): 160 mph
PROJECTED FUEL ECONOMY (C/D est)
EPA city driving: 13 mpg
EPA highway driving: 21 mpg