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2006 Chevrolet Corvette Z06 - Horsepower Helper

An Extra Serving Of Aftermarket Speed Allows This Flambed Z06 To Devour The Competition

Christopher R. Phillip Dec 1, 2009
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What would possess a man to buy a brand-new 2006 Chevrolet Corvette Z06, then re-CNC its heads, swap out its cam, and install a 200-shot of nitrous, all in an effort to push its output to 750 hp? Could it have been passion? Desire? A need for respect?

What if we told you he just wanted to make a great meal . . . out of a Ford GT40?

"I had been reading about the new-for-'06 Corvette Z06 for a while and made the decision to stop by my local dealer in Houston and see one in person," says Greg Wilbur, an information-technology company owner, now residing in Clearwater, Florida. "When I got there and saw it in person, I knew I was going to be driving it off the lot that evening."

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Chevy produced 8,159 Z06s in 2006, all ready to rule the road with the new 427ci, 505hp LS7 engine. According to the press release, the new Z was "the fastest, most powerful car ever offered by Chevrolet and General Motors. And with an unmistakably muscular appearance, the Z06 has a visual attitude that always looks ready to demonstrate Corvette's winning attitude to any challenger around the globe."

Before long, Wilbur was testing the limits of his Corvette, to see if Chevy's press release was true to its word. "I had owned the Vette for about a year and had just finished a date night with my wife, Jessica. On the way back home, I saw an old Ford Cobra ahead of me on the interstate. I proceeded to catch up to him and we ran each other at 50 mph. I beat him by three car lengths, and we both pulled into a gas station to check out each other's rides. As we were talking, a new blue-striped Ford GT pulled into the gas station and came over. Five minutes later, all three of us were lined up, ready to race. I came in second to the GT, and that was when I knew I wanted to take my Z06 to the next level."

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Like Wilbur, other Z06 owners had begun demanding more power from their cars, too. RevXtreme, a Corvette specialty shop in Bradenton, Florida, was among the first to evaluate the LS7's strengths and determine how to squeeze more power out of the highly regarded Gen IV engine. "We looked at the internals of the LS7," company owner Tracy Lewis says. "It already had a high-quality forged-steel crankshaft that could handle gobs of horsepower, the forged titanium connecting rods were extremely strong and lightweight, and the hypereutectic aluminum pistons were well-suited for horsepower. The only issues we saw with them was when they were called upon to perform in high-boost applications."

Confident that the LS7's stock bottom end could easily withstand 700 horsepower or more, Lewis turned his attention to where that horsepower could be hidden: in the cylinder heads, the camshaft grind, and the air-intake system.

He contacted Pete Incaudo, owner of VMax Motorsports in Pinellas Park, whose history in the cylinder-head and camshaft businesses goes back to the 1970s, when he worked with companies like Edelbrock, Air Flow Research, and Comp Cams. Lewis had already worked closely with RevXtreme on the development of several aftermarket performance products for the Corvette and the LS-series engines.

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"When the LS-series motors were introduced in 1997, there were no readily available aftermarket cylinder heads. Incaudo developed a head-modification CNC program based upon improving the intake and exhaust ports of the LS heads. We found the results were fantastic for what we had to work with at the time. Combining his head porting with his knowledge of custom camshaft profiles, we were easily bumping LS1 motors to the 450-500hp range," Lewis says.

"Similarly, when the LS7 first appeared in 2005, Incaudo was one of the first in the country to get his hands on a set of heads," he continues. "From there, he quickly deduced that there was room on the exhaust side for a CNC-porting program to maximize the flow and horsepower capabilities of the casting."

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By the time Wilbur came to RevXtreme with his Z06, Lewis had already modified several Zs with his dyno-proven horsepower packages. Before long, the two men began talking about real power-the kind that would put high-dollar supercars to shame-and Wilbur mentioned the goal he had set after that fateful face-off against the Ford GT. "He said, 'Let's see what we can do to make this much more than the average Z06,'" Lewis recalls. "We put together a proposal for him, and several days later, the project ensued."

First, RevXtreme unanchored the virgin heads from the 6,500-mile Vette and sent them to VMax. Since the intricate port work would take several weeks, RevXtreme had the time it needed to customize Wilbur's Corvette and differentiate it from its factory siblings.

"He wanted to give his Corvette a unique look, without it appearing too gaudy," Lewis says. "We chose a stealth look for the wheels and sent them to powdercoating expert Todd Greene of Fusion Powder Coating in Sarasota. He applied a gloss-black finish, and we painted the caps black with a silver center."

The Corvette's flame-themed exterior was next. "We looked for a paint scheme that would be noticeable, yet subtle, and ultimately decided on a lightly ghosted-flamed design that would make the car appear to be tearing through the sound barrier up in the clouds," Lewis says. "This was done by leaving the base Le Mans Blue Metallic intact, adding the flames in white, and gradually shading blues into it until the design was laid. Then, to tone it down, additional Le Mans Blue was misted over it all until the flames would be difficult to see from any distance-but the closer you come, the more it jumps out."

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Meanwhile, VMax applied its magic to the LS7 heads. "We disassembled and cleaned the heads and valves, CNC-ported the exhaust ports, and hand-ported the intake," Incaudo says. "We also performed a valve job on the hard seats. The intake valve got a 37-degree back angle, and the exhaust valve got a 30-degree cut. To accomplish the 11.4:1 target compression ratio, we angle-milled the head surface, corrected the manifold surface on the heads, and spot faced the head-bolt holes. Finally, we reassembled the heads and valves with a RevXtreme-supplied Patriot dual-spring package."

The second helping of horsepower involved porting the LS7's factory intake manifold. A similar operation (albeit on an LS2 intake) was described in detail in our May '08, issue ("Manifold Destiny"), but we'll let Incaudo provide the following summary: "I start at the throttle-body inlet opening. Then I move to the intake runners, porting the walls and roof back 5 to 6 inches up the runner and blending back another 3 inches, for a total of 8 inches. The intake floor is cleaned and blended with the side walls, and then I polish the complete modification with 60-, 150-, and 240-grit polishing paper."

Incaudo's cam selection was based upon Wilbur's desire to give his Corvette as much power as it could handle without compromising its driveability. "I wanted my wife to be able to drive it comfortably," Wilbur says.

"I chose a custom grind with 232/238-degree duration, 0.608/0.585-inch lift with the factory 1.8-ratio rockers, and a 115-degree lobe-separation angle," Incaudo says. "Admittedly, it's a mild profile, but it allows Wilbur or his wife to drive their Vette cross country one week, then go on a date to the dragstrip the next."

A few additional mods were lavished on the car during reassembly. These included ceramic coating for the existing Kooks long-tube headers, a Corsa 3-inch exhaust system with Twin Series 4-inch tips, and two RevXtreme "signature" items: a 90mm throttle body (mated to a previously installed Callaway Honker cold-air intake) and an oil-separating crankcase-ventilation system.

The biggest mod, however, was yet to come.

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"I wanted to have more power at my fingertips, especially if it's needed for a race," Wilbur says. To that end, he and Lewis selected a Nitrous Express wet-plate system capable of 200 additional horsepower, backed by an MSD digital controller to keep tabs on timing and solenoid activation. Although the unit came with stamped brackets, RevXtreme installed it with custom-fabricated billet-aluminum solenoid brackets to preserve "a quality look" under the hood.

Tuning was performed by RevXtreme's Matt Kesatie. "We started with a base tune file we had already developed for similar builds, so we could have a safe base for initial startup," Lewis says. "From there it was pretty straightforward as we progressed up the rpm range with a conservative tune that would not push the limits. The air/fuel on this car is a flat 12.8:1, and max timing is between 30 and 26 degrees, depending on rpm and engine load. The nitrous controller takes care of the timing automatically when activated, so no second nitrous tune is needed."

To handle the much-improved horsepower, RevXtreme upgraded the Vette's suspension with Pfadt Race Engineering components. "Greg has the Pfadt Aggressor I suspension package, which includes our adjustable coilovers and Competition 'Pfatty' sway bars," says company co-owner Robbin Pfadt. "The Pfadt coilovers are perfect for a car like this because the increase in spring rate makes it more planted in all driving conditions and helps put the horsepower to the pavement. They also offer adjustable damping, so they can be easily tuned with the click of a knob for a variety of conditions.

"The Pfatty sway bars provide more than two times the stiffness of the Z06 units," Pfadt continues. "This makes the car flatter in turns and gives that 'corners like it's on rails' feeling. The reduced body roll also translates into increased responsiveness from the steering wheel. Additionally, the Pfadt bars make the car more neutral in turns, while still allowing excellent traction on corner exit. This is extremely important in real-world situations, like when you want a stable rearend when powering through an off-ramp."

All other mechanical systems on this Vette remain stock, including its T6060 six-speed trans, 3.42 rear gears, and braking system.

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Dyno testing followed the project's completion. "Our testing with heads, cam, and tune resulted in 546 rwhp. When we added the nitrous system, the numbers shot up to 750 hp," Lewis says. In comparison, a stock C6 Z06 will typically pull about 450 hp at the rear wheels.

What's it like to drive a 750hp road rocket on the street? "It takes mad discipline to keep this Corvette at the speed limit," Wilbur says. "It always wants to give me more power, no matter what speed I'm traveling at and no matter what gear I'm in. Next time I see that GT, it's going to be crushed."

So here's a friendly warning to VETTE readers: If you find yourself in Clearwater, Florida, and you glance over and see the subtle look of ghost flames reflecting off the front fenders of an '06 Le Mans Blue Z, think twice before you race it. It just might be Greg Wilbur's modified Z, and the only thing it wants to eat is-you guessed it-you!

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Tampa, FL 33619
VMax Motorsports



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