Lithium-Free Corvette Z06: More Sting for the 2023 Stingray
GM resurrects a legendary nameplate and stuffs it with an all-new flat-plane V8 to advance the Corvette’s cause.
Topping the eighth-generation (C8) 2020-22 Chevrolet Corvette is no mean feat. Customers still pay premiums and patiently wait in line to own one. Yet the new Z06 edition, due next summer as a 2023 model, suggests that the Corvette design and engineering team is just hitting its stride. The Z06 is an ambitious blend of Corvette heritage, state-of-the-art technology – including a new 670-hp DOHC V8 – and lessons learned in racing. This latest member of the C8 family, soon to include two hybrids, is a championship-winning racer tamed just enough for street driving.
Sixty years ago, Corvette patron saint Zora Arkus-Duntov attached the first letter of his name to a sub-rosa component set engineered for racing. Only 199 customers selected the Z06 option ($1,818), making a 1963 Corvette so equipped worth millions today. In 2001, the badge was reprised for the hottest model in the lineup, and Z06s have thrived through three subsequent generations.
New 5.5-L DOHC V8
Sharing only a 90-degree V-angle, 4.40-in (111.8 mm) bore-center spacing and a few fasteners with the immortal ohv small-block, GM’s new “flat-plane” LT6 V8 is a totally fresh design. A horizontally split block secures each main bearing with four bolts. The block and heads are cast aluminum reinforced with cast-iron cylinder liners and valve-seat inserts. A dry-sump lubrication system provides six stages of scavenging and an 8-quart oil capacity.
The star of the LT6 show is a crankshaft with all four throws lying in a single plane (versus the standard approach of four throws spaced at 90-degree intervals). Flat-plane cranks provide 180° of spacing between the exhaust pulses of adjoining cylinders to augment power at the expense of NVH. This approach is standard racing practice, and the reason why exotic Italian sports cars shriek at their red lines rather than emit an American V8 engine’s motorboat rumble.
The LT6 V8’s steel crankshaft, titanium connecting rods and aluminum pistons are all forgings. The four chain-driven overhead camshafts are equipped with phasers to facilitate variable valve timing. Finger followers lie between each cam lobe and its adjoining valve stem. A pair of coil springs closes each valve and lash is set with shims which require no attention throughout the life of the engine. Intake valves are titanium to minimize mass and exhaust valves are sodium-filled for heat resistance.
Combustion chambers yielding a 12.5:1 compression ratio and the engine’s intake ports are all fully machined. A molded-plastic intake plenum equipped with an electronically controlled throttle body feeds each bank of cylinders. Unlike the C8’s LT2 overhead-valve V8, the LT6 does not deactivate cylinders to reduce fuel consumption.
Using a 4.104-in (104.25-mm) bore inhibited coolant flow between the cylinders. The solution – drilling passages through the block’s deck – does provide some lateral flow to cool the very top of each cylinder, according to a GM Propulsion engineer familiar with the LT6 who spoke privately with SAE Media. The LT6’s 3.150-in (80-mm) stroke, originally selected to duck under the international racing displacement limit, yields a net displacement of 5.5L (333 cu in.).
Ready to rip, LT6 delivers remarkable 670 net (per SAE Standard J1349) horsepower at 8400 rpm. The redline is 8600 rpm, while the torque curve peaks with 460 lb-ft (623 Nm) at 6300 rpm. The super-short stroke minimizes the crank’s rotating inertia, expediting the rush to the redline. Though executive chief engineer Tadge Juechter insists Z06 is not a “numbers” car – its official GM-listed top speed is actually slightly slower than that of the conventional Stingray – he does tout a 2.6-second 0-60 mph time.
New Z07 chassis for trackaholics
A superlative chassis is an essential ally in this performance pursuit. While the C8 aluminum spaceframe, control-arm suspensions and magnetic-adjustable dampers are essentially carryover, every variable has been optimized to collaborate with the more aggressive engine and fresh tire and brake specifications. Supplementing the base Z06 hardware, there’s a new Z07 option aimed at hard-core track use.
The Z07 package includes 20x10-in. front wheels wrapped with 275/30ZR-20 tires and 21x13-in. rear wheels fitted with 345/25ZR-21 rubber. Base tires are Michelin Pilot Sport four season run-flat designs while the Z07 package includes stickier Sport Cup summer radials. Skid pad tests revealed that these tires yield 1.22g of lateral grip, according to Chevrolet.
The Brembo-supplied foundation brake system is upgraded with 6-piston (versus four) front brake calipers, larger 14.6-in. front rotors and 15.0-in. rear rotors. Included with Z07 and available standalone are exotic and highly fade-averse carbon-ceramic brake rotors that are 15.7-in diameter in front and 15.3-in. rear. The Z06’s options list also offers carbon-fiber wheels that shave over 10 lb. (4.5 kg) of unsprung weight at each corner.
Exterior and interior uniqueness
To house the Z06’s meatier rolling stock and to cool its more powerful engine, unique fenders and fascias were essential. The new nose cover provides a fifth centrally located radiator while at the rear, exhaust outlets have been pulled inboard from the corners. Side-scoop openings are significantly larger to enhance cooling airflow and overall width is 3.6-in. (9.1-cm) greater to shroud the rear tires.
Extensive wind tunnel and racetrack development yielded major aerodynamic gains, engineers noted. The front splitter is notably larger and the rear spoiler accepts an add-on vertical tab (called a wickerbill) that adds 365 lb. (166 kg) of downforce at high speed. The ultimate choice is an optional package including a larger front splitter, front-corner dive planes, rear under-car strakes and a huge, adjustable carbon-fiber wing. Those aids raise the net downforce to a remarkable 734 lb. (333 kg) at the Z06’s factory-claimed 186 mph (299 km/h) top speed.
In keeping with an anticipated base price of $85,000, the Z06 will come lined with finer materials and offered with new trim choices. There will be seven interior colors coordinated with the dozen available exterior hues and seven different wheel packages. Three seat choices will be available plus two carbon-fiber packages; both the steering wheel and the shift paddles can be wrapped with that racy-looking material.
Juechter’s team invested six years of painstaking effort to make sure that the Z06 succeeds as a supercar without peer. With the exotic brands expeditiously vacating this turf in favor of hybrid and BEV technology, this is the perfect opportunity for the Stingray to advance its cause. There’s no doubt the “Z” in Z06 would appreciate what his successors have wrought.