True to its namesake, the Impala SS introduced at the 1992 Specialty Equipment Market Association (SEMA) show created sufficient stir to warrant a limited production run. And to keep that enthusiasm flowing, Chevrolet/Geo Specialty Vehicles recently trotted out two new Impala Super Sports.
The first—and the most irresponsibly un-green—is the mega-motor Impala SS510. This beast started life as the original SEMA show Impala prototype, but it now boasts a marine-duty Chevy big-block engine that TDM Technologies bored out to an astounding 510 cubic inches and beefed up with Wiseco forged pistons, a Chevy “Bowtie” forged crank, and a Crane cam with roller followers. It breathes through twin LT1 throttle-bodies, a custom intake manifold, stainless tubular headers, and dual three-inch exhaust pipes with Flowmaster mufflers. Output is 546 horsepower at 5500 rpm and 612 pound-feet at 4000 rpm.
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Drivability is not the SS510’s strong suit. Like most hot-cammed heavy-breathers, it idles reluctantly and strains at its leash in mundane commuter duty. But open its twin throats and all hell breaks loose (as do the rear tires on 1–2 upshifts). Even with a beefed up 4L80-E automatic, a Dana 60 positraction rear axle, and huge P335/35ZR-17 tires, launch traction is a limiting factor. Chevy’s own hotshoes whipped it through the quarter in 13.5 seconds at 108 mph in a recent test at Milan Dragway. Our computer simulator, suggests a 0-to-60 time of around 5.5 seconds and a top speed near 165 mph.
The other SS we sampled is the slightly more drivable and equally entertaining Impala Six-Speed. For this one, the Specialty Vehicles group contracted Jack Roush Technologies to build up a ported, polished, balanced, and blueprinted aluminum-head Corvette LT1 engine capable of churning out 308 horsepower at 5300 rpm and 334 pound-feet at 4000 rpm (up from the stock iron-head Impala’s 260 and 330).
All of that is wrung through a Borg Warner T-56 transmission (from the Camaro bin) and a 4.11:1 limited-slip rear axle fitted with a torque arm to prevent axle windup. Other upgrades include adjustable Bilstein shocks, high-performance metallic front brake pads, and the addition of a tiny analog tach.
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When you first settle into the lounge-chair buckets, behind the broad dash and broader hood, a stick shift seems incongruous. But once you’re unmoored, the rip-snorting Winston Cup—inspired exhaust note alters the sensibilities and makes a slushbox seem as inappropriate as it would be in a NASCAR stocker.
Sixty mph flashes by in 6.0 seconds. At 14.6 seconds and 96 mph in the quarter, the six-speed roughly splits the difference between the modern automatic SS’s 15.0-second/92-mph quarter and the original stock SS409’s 14.0 at 98 mph (1961’s best time).
According to Jon Moss, Project Manager of Chevy/Geo Specialty Vehicles, the six-speed Impala will only see production if the GM brass commute the B-body’s 1996 death sentence. The SS510 will be mass-produced when CAFE gets rolled back to 10 mpg and the Sultan of Brunei buys GM. —Frank Markus
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