Hey you! Yeah, you with the '01 Z06. You know Chevy added more power to the '02 Z06, which is rated at 405 horsepower and an even 400 ft-lbs. of torque.And what have you got? A measly 385 horses and 385 ft-lbs. Hardly worth getting excited about, huh?
Don't despair. We found a couple of quick bolt-on goodies from SLP Performance Parts that will bring your "old" Z06 closer to the performance of the latest "oh-six." Better still, if you're even the slightest bit proficient with a socket set and screwdrivers, you can perform these upgrades in your garage.
Working on the proven performance axiom that bringing in more air into an engine and expelling more of it at the other end will boost the motor's overall output, SLP has developed a replacement exhaust system and freer-breathing cold-air intake system for the Z06. (Actually, the parts will fit all C5s from '97 through '02.)
The cold-air system is simple enough-the stock air box and filter are chucked in favor of a large, low-restriction, reusable filter assembly. Developed jointly with filter manufacturer Donaldson, the "Blackwing" air filter snugs up against the mass air meter with the help of an SLP adapter, (The larger mass air meter on '01-02 Corvettes necessitates the adapter. If you slap this filter on a '97-00 model, you won't need the adapter.)
As for the exhaust, a pair of polished 304 stainless steel outlets replaces the muffler system of the Z06. Side-by-side, the SLP exhaust is much smaller and less cumbersome than the factory pieces. Normally, you'd think a great weight savings would be realized, but the stock Z06's titanium "cat-back" assembly is a low-mass marvel. Check out the photos and keep these figures in mind: SLP's exhaust system weighs 26 pounds, while the Z06's titanium system weighs 29 pounds. The stock LS1 exhaust, however, weighs in at 46 pounds. (That's reason enough to swap out an LS1's exhaust, we think.)
Although the scant three-pound savings doesn't sound like much, the SLP "loud mouth" exhaust system certainly does. It comes with removable baffles that, in effect, make the system a straight-through design. With the baffles removed, the system produces a great loud-but-not-too-loud exhaust note. And unlike the deep bass you'd hear with the old-school LT1 small-block, the Z06 sings through these pipes with a higher-pitched, racing-style wail. We thought it was a wholly appropriate sound for the Z06.
When it came to the installation of these new parts, we followed along as SLP performed the operation on a customer's personal car. For comparison purposes, however, we insisted on before-and-after chassis dyno tests. These were performed by independent Detroit-area performance shop White Racing, on its DynoJet.
The stock Z06 spun the rollers to the tune of 332 rear wheel horsepower and 335 ft-lbs of torque. After factoring in a 15 percent drivetrain friction loss between the flywheel and the rear wheels, it seemed our test vehicle was making a few ponies more than the advertised 385. Not too shabby.
The first and easiest swap was the Blackwing air filter. The LS6 welcomed the extra breath of fresh air. Power to the wheels jumped significantly, to a little more than 346, while torque increased to nearly 344 ft-lbs. The simplest bolt-on also proved to provide the biggest sheer gain.
We then turned our attention to the stainless exhaust system, which was tested with and without the included baffles (the SLP air filter was left installed). With the baffles, the exhaust system added four more horsepower. With the baffles removed, the exhaust system was good for eight extra horses and nine ft-lbs. of torque.
When the rollers stopped spinning, our Z06 test vehicle was making an average of 354.8 rear wheel horsepower and 354.6 ft-lbs of torque with the air filter and no baffles in the exhaust. We were surprised how the exhaust and air filter assembly performed.
We didn't expect the air filter to be worth so much and, quite frankly, we thought the exhaust would be worth a little more. (This says something, though, about the inherent efficiency of the stock Corvette exhaust system.) That's not to say we wouldn't recommend SLP's exhaust system. Compare it against other aftermarket systems and we think you'll be hard-pressed to find a freer-flowing, lighter version. Also, the large, polished tips, which nicely emulate the shape of the taillights, add a more finished appearance to the rear of the car. Still, the system did add horsepower and that's the bottom line.
From SLP, expect to pay about $549 for the exhaust, $260 for the Blackwing filter, and another $12.50 for the adapter kit. All told, that's a little more than $800 for almost 25 rear wheel horsepower. We wouldn't do the exhaust system without the Blackwing filter, though.
Still quibbling on whether these bolt-on parts constitute a performance value? Chew on this: Considering the same 15 percent drivetrain friction loss as our '01 Z06 test car, a 405-horse '02 model should make about 345 horses on the chassis dyno. We got to almost 355 for $800; and Chevrolet upped the price of the '02 Z06 over the '01 model by $1450.
Now Playing and Coming AttractionsDesigned to complement the performance improvements gained with the Blackwing air filter and stainless steel exhaust system, SLP also offers a 160-degree thermostat, which simply replaces the stock unit. The lower-temperature thermostat will kick on the electric cooling fan sooner, thereby keeping the engine cooler.
And while the thermostat is already available, SLP is working on a set of stiffer valve springs and higher-ratio rocker arms, which, in effect, work like a slightly higher-lift camshaft to the engine. And thanks to the clever design of the LS1/LS6 engine, the swap is relatively simple. Since the tops of the valve covers are removable, accessing the valvetrain is a breeze. The most exotic tool you'll need is a spring compressor that holds the valve in place from the top of the cylinder head -no biggie.
From what we've been told, the valvetrain parts should be available by the time you read this. When we get the chance, we'll track down our Z06 owner again and see if he's game for another tire-turning session on the DynoJet.
After the exhaust was installed, it was back to the dyno. With the system's baffles in place, the test car picked up just 4 more horses (with the new filter in place). Removing the baffles added another 4, for a final rear wheel output of 354.8 horsepower and 354.6 ft-lbs of torque, gains of 24.8 rear-wheel horsepower and 19.1 ft-lbs of torque for about $800. All this, and a great looking set of polished pipes out back.