You know the type. You’re sitting at a bar, just trying to watch the game while having a beer and eating the free popcorn the bartender dropped in front of you, but there’s that big guy a few seats down who’s being loud and more than a little obnoxious.
He’s not screaming or ranting nonsensically (yet), but you can tell he’s looking for attention. And he’s been drinking for a while, so that attention he seeks probably means he’s ready to throw down, too. So you ignore him, even when the crude comments are begging for a response. Best not to make eye contact, either. It would be all the interaction he needed to start something. Just drink your beer, eat your popcorn, and focus on the television.
Mark Berry’s C7 Z06 is like that lout at the bar. Its ProCharger-fed LT4 grumbles at start up with the same sort of pent-up hostility. Idling is its equivalent of his sitting at the bar—a meaningless exercise in soaking up time, until he can get at you or the next poor guy who accidently brushes against him on the way to the bathroom. Make no mistake, he wants to take it outside right now, and so does Berry’s Z06.
Since the stock blower is integral to the intake manifold, Berry’s car uses a custom LME intake.
There’s another parallel between belligerent bar-guy and Berry’s Vette: alcohol. Rather than bottle after bottle of Budweiser, the Z06 is drinking E85, and you can smell the sharp odor of it on its breath, emanating from the four big exhaust tips. The car sits on drag wheels all around, too, with “skinnies” up front and drag radials wrapped around 15-inch Weld wheels in the rear. It’s like sitting at the bar with your knuckles pre-wrapped for the dustup to come.
There’s no bluster or false bravado here, either. On its first pass down the quarter-mile—a shake-down run—the Z06 blew through the traps at Milan Dragway, outside of Detroit, in 8.87 seconds at 159 mph. We should note that the run was made through the strengthened, but factory-issue, eight-speed automatic transmission and independent rear end. No Turbo-400 or Powerglide, and no stick-axle conversion. Hell, not even the air-conditioning system had been disconnected, and the front shocks were stock.
“That was important to me,” says Berry. “I didn’t want to turn it into a full-on racecar. I wanted a fast car that still drove normally on the street and highway.”
Mission accomplished. Running 8s, however, in a car that could be driven to the track with the A/C blowing through the vents and the Sirius/XM Yacht Rock station blowing through the speakers was no small task. Berry, along with his son, Jeff, turned to longtime racer and builder Don Walsh, Jr., and Justin Haddon, to realize the goal. At first, they dipped their toes before cannonballing into the car’s performance.
“We started basically with a ProCharger and a camshaft change, which was good for 800-and-change [horsepower] at the rear wheels,” says Haddon. “But Mark didn’t even pick up the car after we’d finished the dyno tests. He told us to double down and make some really big power.”
Building Block
Walsh and Haddon regrouped and decided to stretch the LT4 engine, figuratively and literally, starting with the stock block and a Callies 4340-forged crankshaft. This delivered a 4.125-inch stroke, which pushed displacement from 376 cubic inches to a nice, historically appropriate 427 ci—a 12-percent increase in volume that would be packed with more than 20 pounds of boost. The rest of the rotating assembly was commensurately beefed up, too, with forged Gibtec pistons and Callies Ultra I-beam connecting rods. The compression ratio ended up at a comparatively high (for a boosted engine) 9.75:1, but a strict diet of E85 and a sophisticated fuel system would keep piston-burning detonation at bay.
Atop the rebuilt short-block are a pair of CID CNC-ported cylinder heads with 2.7-inch intake runners, along with an LME billet-aluminum intake manifold. And, of course, there’s a supercharger system providing heavily pressurized intake air to the entire assembly. It’s centered around a ProCharger F1A94 head unit, which is good for a whopping 23 pounds of boost. That compressed intake charge flows through a high-capacity air-to-water intercooler, with the water kept nice and chilly via an ice chest in the cargo area.
With the popularity of turbo systems, it was logical to ask why a blower was used for this build. In a word: simplicity.
“I’m a big fan of turbos, but they’re a lot of work,” says Haddon. “On a car like the C7 Corvette, all of the necessary plumbing makes it difficult to package [when you intend] to retain all of its power accessories, air-conditioning system, etc. And with the latest, larger superchargers making comparable boost to turbo systems, it just made a lot of sense.”
Having roughly 1,250 rwhp on tap tends to put traction at a premium.
And let’s be clear—this centrifugally supercharged LT4 makes a lot of power. More than a lot, actually. Something approaching 1,250 hp to the rear wheels, or around 1,500 at the crankshaft.
No Fueling Around
That brings us to the car’s unique, high-volume fuel system, which mimics the factory LT5 setup in the C7 ZR1 by using the factory direct injection (DI) system for lower-speed, lighter-throttle driving, but adds port injection to supplement the DI system when the rpm and boost climb. The design relies on a set of Xtreme-DI injectors, rated at 30-percent higher capacity than the stock units, along with Xtreme-DI’s unique, engine-driven high-pressure fuel pump, which complements the stock camshaft-actuated pump. It was all developed by German transplant and former Bosch engineer Uwe Ostmann, who realized the limits of the direct-injection system in extremely high-horsepower combinations.
“It’s not just about the volume with a DI engine, it’s the pressure that has to be elevated if you’re going to make substantially more power,” says Ostmann. “So, it’s not enough to have higher-flower injectors. You have to support them with the additional fuel pump.”
At the moment, however, there’s a practical limit to what even a pumped-up DI fuel system to do with more engine displacement and 23 pounds of boost. That’s where the supplemental system, with eight 60-lb/hr port injectors kicks in. They’re directed independently via a Holley control system and a custom Crowford harness.
“It all works very well,” says Haddon. “[A high air-fuel ratio] is something this engine can’t afford to experience, and this dual-fuel system does the trick.”
There’s also a nitrous system plumbed into the engine and controlled by the Holley management system, but it hasn’t been employed yet on the track. “To be honest, we’re still sorting out the setup with the engine itself and making sure we’re putting down all the power we can without the nitrous,” says Haddon. “There’s also the ‘what if’ about the transmission surviving, so we’ve been a little reluctant to hit the button.”
Eight is Enough
Berry was adamant about retaining the factory eight-speed automatic to preserve the car’s drivability. “I didn’t want a Turbo-400 or anything like that,” he says. “We had to make it work with the original transmission.”
With only the addition of an extra clutch—which comes from the version of the eight-speed used in GM full-size trucks and more or less slots right into place—and a higher-stall torque converter, the transmission is stock. The rear axle, however, is not. Although it’s still the same independent setup that comes from the factory, it was rebuilt and strengthened by RPM Transmissions and features a 2.56 ratio. That’s a little taller than the stock 2.41 gear, but with all the ratios in the eight-speed, a lot of gear isn’t needed in the axle.
“We’re very careful with the transmission and haven’t tuned out the torque management between shifts,” says Haddon. “It has performed very well with all the power funneling through it.”
Although Haddon feels that running in the 8.80s is an amazing achievement for a street-driven C7 Z06, the car has actually gone even quicker: 8.64 at 162 mph, with the potential to push into the 7s.
“As it sits, there’s probably an 8.50 in it with a little more sorting,” he says. “But a Turbo-400 with a trans brake would probably put it right away in the 8.20s or 8.30s, and the nitrous should drop it into the 7.90s.”
That’s beyond what owner Mark Berry wants from the car right now, preferring to run in the 8s in the afternoon and putter over to the ice-cream stand in the evening. That leaves a little pent-up potential in the package—power looking for an escape route.
It’s like those guys who walk into a bar looking for a fight. They need the emotional outlet. That’s Mark Berry’s Z06. Try not to make eye contact, because you’ll be left with nothing but a bruised ego and the acrid whiff of ethanol as a lasting, humiliating reminder that you should have just minded your own business, and watched the game instead.
