EVERYONE KNOWS THE STANDARD ZR1 IS ONE OF THE FASTEST sports cars money can buy. Propelled by its 638-horsepower LS9 engine, this Corvette can blast through the quarter mile in 11.4 seconds and attain a top speed of 205 mph. It accomplishes these feats while remaining a comfortable street cruiser; it is no one-trick pony. The challenge for those wanting to extract even more performance from the ZR1 is to do so without ruining its drivability. That was Lethal Performance’s aim when it began modifying the ’09 ZR1 on these pages. It wanted to drop the Corvette’s quarter-mile times into the nine-second realm and crack the 200-mph mark in the standing mile without creating a single-purpose race car.
When the silver ZR1 arrived at Lethal’s San Antonio, Texas shop, company owner Danny Gonzales immediately strapped it to the dyno to establish a base line engine-output figure. The number he got was 530 horsepower at the rear wheels. A trip to the drag strip netted a 10.9-second elapsed time at 133 mph, an improvement over the conservative factory figure.
The first change was to upgrade the stock cam to a custom one from Cam Motion. The change was made to improve top-end power as the supercharged 6.2-liter V8 already generated plenty of torque at low rpm. Gonzales estimates the cam change alone added at least 50 horsepower.
Replacing the standard supercharger pulley came next. In went a Lingenfelter Performance Engineering (LPE) unit, which features a 2.6-inch upper. Then came an LPE/ATI crank damper with 14-percent overdrive. Working in conjunction, these devices get the supercharger to spin faster and therefore produce more boost. While these changes allowed the blower itself to remain stock, the engine was now demanding more fuel than the LS9’s stock injectors could provide, so a set of higher-capacity 1,000-cc injectors from Injector Dynamics were installed.
One of the few weak points in the LS9 engine is the intake silencer assembly, which makes a tight turn that slows airflow and therefore robs power. Lethal replaced it with an LPE 4-inch air intake that, teamed with a K&N filter, flows about 45 percent more air. The standard 90-mm throttle body was retained.
To speed up the flow of exhaust gasses, Lethal first added a set of 1-7/8-inch headers, but these weren’t an improvement. They were replaced by a set of American Racing 2-inch headers that Gonzales estimates added 25 horsepower to the total. These were cinched down with ARP header studs.
San Antonio summers are sizzling hot; when daytime temperatures dip below 90 degrees, it feels like spring. To help with engine cooling, Lethal upgraded the radiator to an LG Motorsports Super Cool aluminum unit that’s two inches wider than stock. Making it fit in the car required trimming the shroud. The monster heat exchanger works; Gonzales says temperatures stay in the 170-degree range even on hot days, a 20-degree improvement over stock.