Camshaft and Valvetrain
Selection of the camshaft fell to an aggressive Comp Cams grind, the Xtreme XE-R, with 0.581/0.588-inch lift specs, 224/228 duration specs, and a 114-degree lobe separation. Comp's XE-R grinds are designed primarily for normally aspirated applications, like Wahler's LS2, giving the valves plenty of hang time to ingest air and expel exhaust gases. The Xtreme XE-R cam works particularly well at high rpm, where the LS2 belts out tremendous power with its increased airflow.
The new cam's specs are abstract, however, without comparing them with stock specs. The '02-'04 Z06 factory camshaft, on which the LS2's cam is based, was good for 0.550/0.550-inch lift and 204/218 degrees of duration at 0.050-inch lift. The lobe-separation angle was 117.5 degrees.
With its more aggressive nature, the Comp camshaft gives the LS2 an unmistakable "rump" at idle, sort of reminiscent of an old-school, hear-every-piston-fire big-block. Frankly, it sounds great, but tuning to maintain a good idle quality can be tricky.
The higher-lift characteristics of the camshaft negate the use of stock valvetrain components, including the rocker arms and springs. Stiffer double-style springs and 1.7-ratio roller rocker arms, all from Comp, were installed.
Intake and Exhaust
This modified LS2 draws its breath through a Halltech Stinger cold-air intake system, sending the air to a modified FAST LSX intake manifold, modified by A&A Corvette Performance to fit better beneath the C6 hood. The Halltech intake keeps the mass-air sensor in roughly the stock location, so air metering and tuning issues are negligible to nonexistent.
While comparisons with a FAST intake and a factory intake may show little difference on a stock engine, the airflow advantage is clearly evident on a modified engine such as this one. The FAST intake, like the new camshaft, really shines at higher rpm, providing not only an increased volume of air, compared with the stock intake, but excellent velocity.
While the intake system supports the airflow into the engine, a set of LG Motorsports Pro long-tube headers backs up the engine's exhaust-expelling requirements. These are monster, stainless steel headers, with 1.75-inch primary tubes that stretch 32 inches in length. And while not CARB-certified, they may be configured, as Wahler's car is, with high-flow cats mounted to a 3-inch X-pipe.
Along with the heads, cam, and intake/exhaust mods, Wahler's Corvette also received an ASP underdrive pulley, a 160-degree thermostat, and a pair of Corsa's free-flowing, great-sounding Sport mufflers. The whole package was installed at Rev Xtreme, with tuning performed by Jeremy Formato.
"Every car is different, but our experience with these head-and-cam packages means we can usually get the tuning done in two or three hours," said Clark. "Idle quality on Robin's car is great; it's his daily driver, so a good idle was a must."
The engine's 311-rwhp baseline performance was typical for an automatic C6, but Clark says the car's final 443-rwhp output was actually a bit lower than it might have been under different circumstances. "We installed a looser converter, with a stall speed of about 3,200-3,600 rpm," he said. "That always masks horsepower on the dyno. The car is probably putting out about 460 hp through the tires on the street."
That's considerably more than the street output of the vaunted Z06. For those whose checkbook balance won't quite stretch to nearly $66,000, Rev Xtreme's simple, but effective, heads-and-cam combo proves there are more economical ways to have the fastest Vette on the block.