The Corvette crew must have been biting lips bloody to keep this secret from leaking. The C6, the Porsche-baiting sixth-generation Vette, is a fine rejuvenation of America's favorite sports car but a mere Wilbur Milquetoast compared with the next project in the hopper. For those of you who are unimpressed by the C6's 400 hp and 186-mph top end, your redemption is nigh. At year's end, the Z06 son of C6 hits the streets with Porsche's 911 Turbo in its crosshairs.
Challenging one of the most revered nameplates in sports-cardom with a car that has a pushrod engine sited far from the drive wheels is no mean feat. The Corvette folks prepped for that mission by lightening everything but the brakes, by hogging out the cylinder bores, and by nudging the redline ever higher. Other than wheelbase, little of the C6 makes the leap to the Z06. What we have here is an all-new engine, major body alterations, sweeping chassis mods, and true supercar materials throughout. Calling it the Z07 would have been warranted.
THE ENGINE
The Jack LaLanne of the engine world, GM's small-block V-8, ripples with newfound muscle thanks to a fatter bore and a longer stroke that yield 428 cubic inches or 7.0 liters of piston displacement. Coded LS7 (in 1970, GM advertised a 460-hp LS7 big-block V-8 that was never bolted into a production car), the latest Z06's engine consists of a new aluminum-block casting liberally loaded with go-fast goodies. A forged-steel crankshaft is supported by six-bolt forged-steel main-bearing caps and is twisted by forged-titanium connecting rods that are 25 percent lighter than the ferrous-metal rods used in the standard 6.0-liter V-8. Lighter cast-aluminum pistons sliding inside pressed-in cast-iron cylinder liners hammer the incoming charge with an 11.0:1 compression ratio. Intake and exhaust valves are lined up edge-to-edge, wall-to-wall. The 2.20-inch-diameter intakes are titanium for weight savings, and the 1.61-inch exhausts are sodium-filled for rapid heat transfer. An aggressive roller-follower camshaft kicks the valves open 13 percent wider than in the 6.0-liter V-8. All critical cylinder-head surfaces-intake and exhaust ports, combustion chambers-are fully machined to surpass the 6.0-liter engine's airflow by 18 percent. An electronically controlled 3.5-inch (90-millimeter) throttle meters air to the composite-plastic, tuned-length intake manifold, which is fed fuel by high-capacity solenoid injectors. On the exhaust side, four hydroformed stainless-steel tubes merge into one wide-mouth catalytic converter per bank.
The pice de rsistance is a bona fide dry-sump lubrication system-a feature Porsche eliminated from its flat-sixes to save cost. A gerotor-type pump driven by the crankshaft evacuates oil that drains to the bottom of the block for storage in a cylindrical reservoir positioned in the right rear corner of the engine bay. A second pressure pump draws lubricant from the tank for delivery to the engine's oil galleries. The key benefit with this arrangement is that there's no chance of oil starvation when high revs mix with high-g cornering and braking. Oil capacity is greater by 2.5 quarts (8.0 versus 5.5 in regular Corvettes), and the remote reservoir helps remove trapped air from the lubricant. To clear a spot for the tank, the battery has been relocated behind the right rear wheel.
The LS7 generates a husky 500 hp at 6200 rpm, with a torque curve humped up to 475 lb-ft at 4800 rpm. That's 3.6 times the output of the original "Turbo-Fire V-8" engine that debuted in '55 Chevys, showing just how far a sound idea can go with half a century of development.
THE CHASSIS
Although the Z06's 500-hp news was too much to contain, Corvette keepers did successfully hide the fact that the hot engine would be carried by a new aluminum spaceframe. In comparison with steel, aluminum has one-third the density and half the yield strength, so substituting one for the other in a thoughtful manner can deliver substantial weight savings. In place of hydroformed and stamped pieces of steel, the Z06's spaceframe is an amalgamation of hydroformed and extruded aluminum components, stamped panels, and a few castings (used to reinforce suspension mounting points). That alone trims 135 pounds, but chassis engineers went further by switching the aluminum front crossmember assembly to a magnesium casting. Magnesium is a third lighter than aluminum.
Trimming weight was costly but essential because of mass additions crucial to the Z06's cause. Beyond the dry-sump oil system, extra pounds come with the new three-inch-diameter exhaust system, a lubricant-cooling circuit added to the differential, wheel rims that are wider by an inch in front and two inches in the rear, and wider-section 275/35ZR-18 front and 325/30ZR-19 rear Goodyear Eagle F1 run-flat tires. The brakes-one place where mass is desirable-are also larger. New monoblock front calipers squeeze six separate brake pads per wheel against cross-drilled and radially vented rotors that are 0.6 inch larger in diameter than in a C6 with the optional Z51 performance package. At the rear, there are four pads per wheel and 0.4-inch-larger rotors. ...next page >>