Power Play

In the high-performance sports car world, there is no such thing as standing still. Sports car manufacturers around the world must constantly up their game to remain atop the conversation. Yet the Chevrolet Corvette, soon to mark 70 years since production began, seems to have a regular place there.

Case in point: Just three years after the introduction of the first production mid-engine Corvette, and with demand still high, comes the newest evolution of the Corvette. That, of course, is the all-new 2023 Z06. It was co-developed with the C8.R, which has already won two International Motor Sports Association (IMSA) GTLM Manufacturers Championships.

“There was a niche following of customers,” says Corvette executive chief engineer Tadge Juechter, “that really pined for the immediate response, light weight, and the visceral feel that would exceed the previous-generation supercharged Z06. But what kind of powertrain would we need? The only way to do that is to create the highest-horsepower naturally aspirated production V8 that’s ever been done in world history. That’s what had to happen.”

And happen it did.

But the amazing thing is that the powertrain engineering team did it with a smaller displacement engine (5.5-liter versus 6.2).

Besides its all-new dual overhead cam valvetrain, the big secret of the Z06’s 5.5-liter engine is a flat-plane crankshaft. Compared to a V8 with a cross-plane crank, a flat-plane crank can rev higher, and for enthusiasts, that’s reason enough. Glorious sound and stunning performance are the payoffs.

How does a flat-plane crank differ from the more typical cross-plane crankshafts? Flat-plane crankshaft rod journals — where the connecting rods attach — are 180 degrees apart when viewed from the end of the crankshaft, versus 90 degrees apart in a cross-plane crankshaft. That means the engine’s firing order alternates back-and-forth between the two banks of cylinders, helping increase exhaust airflow efficiency. The construction of a flat-plane crankshaft also requires less counterweighting, lowering inertia to help the engine quickly rev to 8600 rpm. Plus, a shorter stroke and wider bore help the engine rev faster.

“An engine of this nature is truly playing in the exotic space,” says Dustin Gardner, assistant chief engineer, LT6 engine.

“It is a low-volume, hand-built precision engine,” adds Gardner. “The biggest advantage of the flat-plane crank is that the mass of the engine that moves is much lighter. It allows the engine to accelerate to speed much more rapidly than a small-block.”

The exhaust system was completely reinvented, with four outlets grouped at the center of the rear fascia. Even the exhaust tips were given a parabolic shape to reflect more sound back to the driver. The result is a higher-pitched sound than a traditional V8.

What it all means is 670 horsepower, 460 pound-feet of torque, and an 8600-rpm rev limit.

Even though it is only 5.5 liters of displacement, the LT6’s power output exceeds the 650-horsepower number of the 6.2-liter supercharged engine powering the seventh-generation Z06. 

Those three special alphanumeric characters date back to 1963, when the split-window Sting Ray was introduced. “Z06 was a code for a track-oriented performance option” for the second-generation Corvette, says Juechter. “Only 199 were built. It wasn’t until the fifth generation that we brought it back and it became a brand unto itself.”

The original Z06 offered all the heavier-duty racing hardware that potential racers were seeking, plus a huge 36-gallon gas tank for longer endurance events. “It’s the most track-oriented Corvette that we do,” Juechter says. “During the fifth, sixth, seventh, and now eighth generation, we have moved the street car and the race car closer and closer together.”