If NASCAR had stricter homologation rules, Dale Earnhardt Jr. would be lapping Daytona in a front-drive four-door with V6 power. Alternatively, I suppose, your mother-in-law could cruise to the Piggly Wiggly in a tube-framed coupe with a live axle and a giant, four-barrel-fed V8.
Homologation requirements dictate how closely related a given racecar has to be to its roadgoing (purported) equivalent, and there's plenty of variety between various series when making those calls. In NASCAR, to race as a Ford or a Chevy pretty much just means slapping the appropriate grille-shaped decal onto the hood; in SCCA Spec Miata, some cars still carry their original license plates.
The closer a competition environment gets to making racecars remain true to their streetbound forebears, the more any manufacturer must either accept street-specific hardware on its track cars or give its production cars trackworthy goodies. The latter is obviously more enticing to the car-buying public, but it all can get taken too far. Street-legal "homologation specials" often end up being so expensive that no one can actually buy them, thereby defeating the whole purpose of street-car-based racing.
For most of Corvette history, a conflicted approach to motorsports?and therefore to cool homologation cars?has been an all-too-familiar bugbear. The Corvette Grand Sport of the early '60s is the most famous example, promising as it did the supercar to end all '60s supercars but delivering just a wistful what-if. Had the proposed 100+ streetable copies been built as FIA racing rules then required, it's reasonable to assume that street Corvettes might have been changed to this day. (Not that the Chevrolet camp probably intended to honor those totals in any case. Enzo Ferrari always played fast and loose with the FIA inspectors, so Zora Duntov is unlikely to have done any different.)
Regardless, while Corvette fans dreamed of Grand Sport homologation replicas, GM management wouldn't countenance even five cars, let alone 100 or more. As Corvette historian Karl Ludvigsen quoted GM chairman Frederic Donner saying in '64, "[Racing cars] are very different, however similar their names, from the cars built for sale to the general public?. They must possess qualities which aren't the same as those that the majority of the buying public seek in a car."
Such timidity didn't affect Donner's counterparts over at Ford. Later that same decade, the Dearborn crew tossed that narrow-minded stance out the window with the GT40 and went on to win Le Mans four times straight. The mid-engined miracle first ran as an unhomologated prototype, but eventually qualified itself as a production car thanks in part to a number of roadgoing copies.
Fast-forward to '05, when a mid-engined Ford with warmed-over GT40 lines has already been the darling of show stands and magazine covers for going on a year. Even the next-generation Corvette can't get as much play as the semi-serious Ford GT, but that's finally about to change: The new Z06 has arrived, and it's going to keep the '60s from happening all over again.
Corvette history, of course, has taken some much better turns since the era of Frederic Donner. The second half of the C4 generation, for example, saw Chevy re-embrace factory-backed racing with its very own series, the Corvette Challenge. Shortly thereafter, a limited-run supercar arrived in the form of the ZR1, followed by the FIA-legal (and eventually Le Mans-winning) C5R racer a decade later. Cap it all off with the low-volume Z06 of 2001-'04, and things must be looking up.
With the arrival of the C6, Corvette engineers got a nearly clean slate from which to create the next round of such street and racing successes, and the upcoming C6R and Z06 are the result. Indeed, the development teams elected to create the two virtually side-by-side, throwing away the notion that racecars and road cars must have little in common. Instead, this program proved that the goals of a sports car for both road and track could be furthered by studying them together.
The C6R is an extension of the highly successful C5R, while the Z06 is intended to be part supercar, part brand flagship, and part homologation special. And since neither machine had to fly under the radar this time (unlike the old Grand Sport) they were both free to take full advantage of the resources and skills of the whole corporation. More to the point, they could add to them.
In the car industry as a whole, the dream of a symbiotic relationship between street cars and track cars is nothing new. The reality is another matter, but the next Z06 could be the closest thing that Detroit has yet seen to this fantasy becoming fact.
One reason, obviously, for sharing the latest ideas between street cars and race cars is to "bring even more technology to the street for our customers," in the words of Corvette chief engineer Dave Hill. Yet while the idea that GM ever provides the best of anything out of sheer enthusiasm seems hard to swallow, Hill's most recent creations actually argue this point pretty well. Every boast about integrated race technology, state-of-the-art components, and specially developed hardware is verified just by looking.
The 2006 Z06 is constructed around a perimeter-style frame just like other Corvettes, but the main rails beneath it are hydroformed out of aluminum instead of steel. The front engine cradle on the street car is made of lightweight and robust magnesium. And where the final year of the old Z06 included a carbon-fiber hood largely for commemorative-edition fanfare, the new Z06 takes advantage of that exercise by including carbon-fiber front fenders and wheelhouses plus sheet-carbon floorboards surrounding the model's traditional balsa-wood core. There's a lightweight, non-removable magnesium roof panel that simultaneously lower the Cg and greatly increases rigidity. And despite the addition of numerous beefier, heavier performance components such as larger brakes, heavier antiroll bars, and wider wheels, the 2006 Z06 weighs nearly 50 pounds less than the standard C6 (or some 3130 total) thanks to the extensive use of advanced chassis and body materials.
On the outside, the Z06 body includes several visual updates to separate this FIA stalking horse from the cooking C6. The more obvious changes include a central hood intake, flared wheelarches stretching a full three inches wider than standard, cooling ducts for the rear brakes, stouter front-fender vents, and reworked nose and tail caps. It's a relatively short list of differences, but the changes are substantial enough to ensure that the new Z06 stands out even more than the much loved C5 version. On the inside, unique lighter, grippier leather seats are joined by a smaller and much more attractive three-spoke wheel, standard HUD and air conditioning, and reduced sound insulation.
Still, like its predecessor, the majority of the upgrades have taken place underneath, starting as always in the engine compartment. Followers of the C5R racing effort are well aware of that car's potent powerplant, a bored-and-stroked interpretation of the familiar Gen-III V8. With a huge 4.125-inch bore and four-inch stroke giving a Rat-sized 427 inches of displacement, the "smallblock" designation was somewhat of a misnomer for that engine, even though it retained the same external dimensions as its LS1/LS6 forebears.
That same 427 is slated to continue in the C6R, but thanks to the much closer relationship between road and race trim demanded by new FIA/ACO/ALMS rules, the roadgoing Z06 will get its own 427 (Mat-motor? Rouse-motor?) for 2006. The numbers are nothing short of staggering: a full 500 horses at 6200 rpm, 475 lbs-ft @ 4800, a sub-four 0-60 dash, and quarter-mile sprints in under 12 seconds?a set of bogus plates and a false identity card would be nice additions to the glovebox. Despite being essentially a re-thought race motor, this new Z06 mill (called LS7 by GM) also promises remarkable tractability, thanks to receiving the same level of engine-management attention given its junior cousins.
While its exterior dimensions and general layout are shared with the LS2, the new LS7 is based on a separate block casting and assembled by hand at GM's new Performance Build Center in Wixom MI. The punched-out aluminum block carries lightweight titanium conrods attached to aluminum flat-top pistons giving 11.0:1 compression. Six-bolt, CNC-machined, forged-steel main caps are needed to keep the assembly together.
CNC machining is also utilized on the new aluminum heads, which boast an 18% improvement in airflow over LS2 units. Nearly straight tunnel-like intake runners feed the air/fuel charge through huge 2.2-inch titanium intake valves while 1.62-inch, sodium-filled hollow exhaust valves let spent gasses back out. A hydraulic-roller cam provides a significant .591-inch lift, even before taking into account the super-high-ratio rocker arms.
As on the C6R's race engine, hydroformed four-into-one tubular headers carry the exhaust from the heads, after which it's routed into a model-unique set of catalytic converters and dual-mode mufflers. The latter include a vacuum-operated valve that stays closed at low revs to manage noise and opens at larger throttle angles for minimum backpressure. The engine is lubricated by racing-style dry-sump oiling, which ensures complete lubrication under all cornering loads. Despite the massive displacement, lightweight internals give the LS7 a 7000-rpm redline in roadgoing trim?a figure more commonly associated with multivalve twincam Fours than traditional pushrod V8s.
The LS7's significant output is channeled through a lightweight flywheel and clutch assembly feeding a strengthened version of the previous model's Tremec six-speed transaxle. This rear-mounted gearbox includes a pump that routes transmission fluid through the front radiator stack for additional cooling, after which the chilled fluid is also used to help cool the lubricant in the limited-slip diff on the way back. The latter unit features an enlarged ring-and-pinion assembly and turns upgraded halfshafts and U-joints.
Huge 325/30ZR19 rear Goodyears put the power to the ground; the matching Eagle F1 Supercars up front are 275/35ZR18s. These ride on Z06-specific split-spoke alloys measuring 18x9.5 front and an imposing 19x12 at the rear. The basic suspension layout is shared with the standard Corvette, but performance-directed upsizing of the spring rates, antiroll-bar diameters, and braking hardware sets the Z06 apart. The stopping is done by 14-inch vented and crossdrilled rotors up front and 13.4-inch pieces out back, an increase of more than an inch at both ends. New six-piston calipers in front and four-piston units in back handle the clamping needs.
Corvette enthusiasts will undoubtedly applaud the comprehensive component list associated with the new Z06, but all that hardware is certain to come with a price. While the previous Z06 was able to hit showroom floors with a very digestible sticker thanks to its focus on just a few well-placed modifications, the more complete package that comes with the C6 version will inevitably equate to a tougher-to-swallow tariff.
Chevy insiders have sworn on their dead grandmothers' graves that the base Porsche 911 price was the program's target, yet it's hard to believe all that carbon, aluminum, and other specialized hardware can really be delivered in the high-60s; even a $75,000 sticker would be a spectacular value, especially compared to the six-figure tab of the Ford GT. On the other hand, anything more than that sum is likely to raise unfortunate accusations of ZR1-itis?it's hard to see how Chevy can win either way.
Providing cutting-edge hardware to the always-loyal Corvette fans appears to have played a key role in the new Z06's formula, but GM's renewed dedication to racing carries most of the drive for this Corvette supercar. Not that it really matters?either one of these motivating factors would be cause for celebration, especially given the praise heaped on the marque's glamourous heroes of yesteryear. It's great to admire the Grand Sport and L88, but neither of those legends was the result of such a legitimate street/track partnership, and neither one's nearly this fast.
The Corvette family's fastest street car and fastest racecar now have more commonalities than differences: seven-liter powerplant, dry-sump oiling, lightweight chassis, carbon-fiber bodywork. In the more restrictive environment of 2005's racing rules that was inevitable, but GM could have just as easily chosen to downgrade the C6R or cease racing altogether. This time around the company has decided to do what's best for both the street and the track. History ought to be doubly kind to any Corvette that comes out of that."
