First Drive Review
Let's call it the Corvette 5.5, as the 2002 405-horsepower Z06 is the fifth opportunity in five years to unload valuable pesos on the latest and greatest Corvette. If you own a Corvette "5.4," the 2001 385-horse Z06, it is now on a depreciation schedule akin to that of an IBM Selectric. Asked why GM would sell 7400 vehicles knowing they would be obsolete within 14 months, Corvette chief engineer Dave Hill said the 5.5's upgrades weren't ready then and that the company doesn't sell wine before its time. Hope that helps . . . Just as the Corvette 5.4 was when it was introduced last year, the Corvette 5.5 is faster, with more installed technology. It will also cost more when it hits stores at the end of the summer, although exactly how much more GM has not said as of this writing.
The 5.5 is expected to cost $1000 to $2000 more than the Corvette 5.4, which has a base price of $49,128. Thus, the 5.5 will be the most expensive stock Corvette in circulation. The biggest change 5.5 users will notice is the revised LS6 V-8, whose output has risen by 20 horsepower to 405 at 6000 rpm and by 15 pound-feet of torque to 400 at 4800 rpm. Almost all the added power is at 3500 or higher rpm, while the redline remains unchanged at 6500 rpm. About half the horsepower increase comes from a lumpier camshaft that pushes intake-valve lift by 0.7 millimeter to 14mm and exhaust lift by 0.5mm to 13.9mm.
To handle the change, assistant chief engineer John Juriga and his crew added fortified valve springs and lightweight hollow-stem valves, a feature last seen on a Corvette in the late ZR-1's twin-cam LT5 V-8. The valve stems are drilled with walls just 0.8mm thick, topped up with a sodium-potassium mix that helps dissipate heat, and then spun at high revolutions to friction-weld a cap on. At about $8 apiece, they are five times the price of the old solid-stem valves. Otherwise, Juriga and company left the LS6's cylinder heads alone, making changes upstream and downstream to eke out small improvements. A redesigned filter box in the nose flows more air more smoothly, allowing engineers to dispense with the mass airflow meter's honeycomb "air straightening" screen.
All of that is worth about five stallions, while another five come from removing the two small manifold catalysts that helped the Corvette 5.4 pass federal smog tests. Juriga says the precatalysts, worth 5.5 pounds and an inch of mercury each in back pressure, aren't needed to meet the standards now that redesigned underfloor catalysts are in place. The Corvette 5.4's fabulous titanium mufflers remain standard equipment. Gracing the front axle is a thicker anti-roll bar with aluminum links. The curb-to-curb turning circle shrinks by 2.1 feet to 40.2. The rear shocks are recalibrated to provide more compliance over corrugated pavement but slightly more resistance to low-frequency motion such as acceleration squat and transitional body roll.
The Corvette 5.5 also rides on new spin-cast alloy wheels from Speedline, replacing last year's identically styled forged units. Sadly, magnesium wheels are no longer an option on any Corvette. GM claims a 12-pound decrease in the Z06's curb weight to 3118 pounds, in part due to the lighter Speedline wheels. The head-up display, not available on the Corvette 5.4, is standard on the 5.5. So is a CD player. Dark Bowling Green Metallic, last year's least popular color and only available on Corvettes 5.1 and 5.2, is gone, replaced by the Electron Blue, which will be available on all versions.
GM says the Corvette 5.5 will reach 60 mph in less than four seconds and polish off the quarter-mile in 12.4 seconds. Considering we've had trouble slipping 460-hp Vipers under the four-second mark and that a Z06 has never hit 60 in less than 4.3 seconds by our hands or reached 1320 feet in less than 12.7 seconds, it's possible we won't be able to substantiate these claims. The fact that the Corvette 5.5 may be only slightly faster than the 5.4 will be of little comfort to 2001 Z06 owners, whose identity will soon be made obvious to everyone by the new fender badges with "Z06 405 HP" written on them. True, GM isn't offering any free upgrades, but if you really bitch, perhaps it'll send you two of those.
