Conversion Machine

Also from Issue 82

  • 2014 Stingray Convertible
  • The Last C6: 2013 427 Convertible
  • Interview: Dave Tatman
  • Buyer’s Guide: C5
  • Amelia Island Sting Ray Salute
  • Profile: Dave McLellan
  • 1962 Restomod
  • Corvette Racing: Data Acquisition
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Contributing to the Z06’s incredible performance at the drag strip was its light weight. Though the hardtop coupe upon which it was based was already the lightest car in the Corvette lineup, Chevy took further mass-reducing measures. The entire exhaust system rearward of the catalytic converters was constructed of titanium. The Z06 got a special battery that weighed 5.7 pounds less than the standard version, as well as a smaller brake pressure modulator. Chevy even went so far as to fit the Z06 with a thinner windshield and backlight. At 3,130 pounds, it weighed 99 pounds less than an ’01 coupe. To prevent customers from piling on the pounds with options, the Z06 could not be had with fog lights, a head-up display, a telescoping steering column or passenger-side power seat.

The Z06’s lower mass also helped it in the handling department, but Chevy wasn’t content with simply equipping it with the Z51 package as it had been with the hardtop. Instead, the Z06 got its own unique suspension setup. Compared to the standard Z51 kit, the Z06’s FE4 package featured stiffer front and rear springs, a larger-diameter front anti-roll bar (30 mm versus 28.6) and wider-diameter Bilstein shocks (45 mm versus 36 mm). The Z06’s rolling stock was also upgraded, with forged alloy wheels (9.5 × 17-inch front, 10.5 × 18-inch rear) and specially formulated Goodyear tires (245/45ZR17 front, 275/40ZR18 rear). Because this sticky, unidirectional Eagle F1 SC rubber did not have run-flat capability and engineers were loathe to fit the Z06 with a heavy spare tire, the car got a can of fix-a-flat instead. To optimize the size of the tires’ contact patch, the Z06 received unique wheel alignment specifications with half a degree of additional negative camber. The Z06 could generate a supercar-like 1.03 g of lateral acceleration around the skidpad.

To increase braking performance, the size of the rear brake rotors was increased from 12.0 in 12.6 inches, while the addition of air scoops just in front of the rear-wheel openings helped keep them cool. Combined, this long list of upgrades made the Z06 the most track-capable Corvette Chevy had ever offered, one that handily outperformed the C4 ZR-1 at a price point ($47,500) that was $20K lower.

Not surprisingly, the ’01 Z06 was a sales success. Chevy sold 5,773 of them, and would have sold more if wheel-supply problems had not limited production. Yet the carmaker did more than just find a new rim outfitter for the 2002 model year—in this case Speedline, which developed a cast wheel that was just as strong as the forged one—it managed to extract an extra 20 horsepower from the LS6 engine and performed a small suspension tweak.

As it turns out, GM powertrain engineers weren’t quite done with the LS6 when the Z06 debuted for the 2001 model year. They had run out of time to optimize the valvetrain and maximize engine breathing. The first step was to revise the catalytic converters. The new ones reduced back pressure and allowed the engine to flow more air; a larger opening in the air box helped as well. This, in turn, allowed the use of a more aggressive, high-lift camshaft. To keep pace with the cam, lighter, hollow-stem valves were fitted, as were stiffer valve springs.

In the end, the 2002-spec LS6 generated 405 horsepower at 6,000 rpm and 400 lbs-ft of torque at 4,800 rpm. That works out to 70.1 horsepower per liter, which simply blows away the 57.4 horsepower-per-liter figure for the ’71 LS6. In celebration of its accomplishment, Chevy festooned the car’s front fenders with “Z06/405 horsepower” plaques. It also provided the car with revised performance figures: The Z06 could now dash from zero to 60 mph in 3.9 seconds and cover the quarter mile in a fleet 12.4 seconds.

These improvements at the test track weren’t gained through increased engine output alone. By re-valving the rear shocks, engineers were able to reduce wheel hop at launch, helping the tires to hook up more quickly. This revision was also aimed at making the Z06 less jittery on bumpy backroads.

During our brief time behind the wheel of MacKinnon’s Z06, it certainly felt planted in the corners. Its ride was stiff, but never harsh or brittle. Our biggest impression, however, was of the car’s speed; it felt damn fast. Between the incredibly eager-to-rev LS6 and the low gearing, this car flat-out bolted whenever we got on the gas. While the 505-hp 7.0-liter LS7 that powers the C6 Z06 deserves all the accolades it has received, we think the 405-hp LS6 is underappreciated. In some ways, the LS6 is more responsive; it seems that you get into the meat of its powerband more quickly than with the LS7. Taller gearing plays a role in this, something that also affects acceleration. As a result, both Z06s post the same zero-to-60 mph time, and the newer C6 version is hardly any quicker down the quarter. Autocrossers actually prefer the older model.

MacKinnon certainly sees no reason to make any changes to his Z06, nor does he forsee selling it any time soon. He’s put roughly 10,000 miles on the Corvette since he bought it, driving it to work about 50 percent of the time. “It’s a perfectly satisfying car as a commuter,” says MacKinnon. Though he’s gone on a few NCCA rallies, including one to Oregon, what he really loves to do is get his car on track. He learned his chops at Thunderhill Raceway Park, where he completed a couple of Northern California Racing Club driving schools. Naturally, given his line of work, he is rather interested in exploring the physics of the racing line.

MacKinnon is particularly fond of Mazda Raceway Laguna Seca, which is where we caught up with him for our photo shoot. With his pal Robinson offering up the occasional pointer, MacKinnon posted some respectable lap times. He is quick to give credit to the car, however, saying that its abilities still far exceed his own. Though his wife has yet to warm up to the car, MacKinnon has been very pleased with his Z06. “Couldn’t be happier with it,” he says. Speaking like a true Corvette convert, MacKinnon adds, “The C7 looks like a fantastic car, but I would have to give up the C5 to buy one—plus, I’d have to make sure it found a good home.”