On a third glance, you might catch the subtle "Supercharged" graphic on the decklid, but it's probably too late by then. The boost is in full swing and you're left holding your shifter in your hand and wondering what just happened to that four-door tub that seemed so innocent.
That's really the goal of a sleeper, and while Colorado Springs residents Jeff and Dawn Wendling may have just wanted to preserve the Impala SS's good looks, they added a mountain of horsepower not typically associated with Chevy's last rear-wheel-drive sedan.
Jeff, a 44-year-old integrated system technician, purchased his pride and joy in 1997, and he wasted no time in modifying it. Jeff's son Mike performed most of the work at RMCR Performance in Colorado Springs, where he works as a master technician. With a mere 1,500 miles showing on the odometer, Mike tossed on a Vortech S-Trim supercharger, Borla exhaust system and AS&M headers. At an average altitude of 6,000 feet, the air where the Wendlings live is not exactly optimal for horsepower, but the huffer motivated the behemoth in a big way. These mods were followed by a Vigilante torque converter, which enabled the Impy to scoot down the quarter mile to the tune of low 13s.
Jeff drove the Impala in this configuration for 20,000 miles. "We were pushing 10psi on the stock motor," Jeff said, "so I decided to tear it down before something catastrophic happened." What ensued was nothing short of a gearhead's dream.
Mark McCallon, RMCR's president, handled the engine assembly which included a .020 overbore of the block, followed by SRP pistons, Summit Racing's Pro Light I-beam connecting rods and the stock crankshaft. The RMCR staff also race-ported a set of LT4 cylinder heads and gave them a five-angle valve job. 2.00 intake and 1.55 exhaust valves receive air from an LT4 intake manifold, and fuel from a set of Ford Racing 30 lb./hr. injectors. Mike prefers the impedance rates of the small injectors and compensated for their flow rate with a Bell Engineering fuel management unit.
Conducting the where to go and what to do chores is a custom RMCR-spec Competition Cams bumpstick, which offers a duration of 210 degrees intake/220 degrees exhaust at .050, along with .507-inch lift on a 114-degree centerline. Comp's 1.6:1 roller rockers work in concert with an AFR Rev kit to keep the air moving in and the exhaust moving out. The aforementioned Arizona Speed and Marine was sourced for the 1 5/8-inch, equal-length headers, which are connected to the stock catalytic converters for the street, and straight-through pipes for the track. These are followed by the burbling Borla catback system.
The Vortech S-Trim was upgraded to a T-Trim model for more boost, but Mike and his RMCR band of brothers looked to improve the efficiency of the supercharger by adding an aftercooler. Originally a Vortech unit, RMCR modified the intercooler to work with the Impala engine compartment structure. A Vortech Maxflow race bypass valve is also employed, but the huffer is just one of the power adders on board. Jeff also has a Nitrous Express EFI single-stage nitrous system with all the bells and whistles that's worth an extra 75 horsepower at the touch of a button.
RMCR also handled the transmission rebuild. Since Jeff feared for the stock short-block, certainly the automatic box would need some beefing. Therefore Level 10 Kevlar clutches, Kolene steels and a billet servo were added to the TransGo shift kit to make sure minimal power was lost between shifts. A Precision Industries 2500-stall converter helps get the Chevy off the line and also speeds the arrival of boost. Out back, the Impala's stock rear end has been fitted with a G2 Motorsports girdle and a set of 3.73 gears, although Mike told us that a Ford 9-inch would soon replace the ailing GM unit.
What was all of this heavy mechanical labor worth? How does 532 rear-wheel horsepower on 91-octane pump gas sound? At Bandimere Speedway in Denver, with 5,800 feet of altitude, the Impala went 12.00 at 117 mph with a 1.7-second short time. And the car still only has 34,000 miles on it. All outward appearances would suggest that this Chevy has been given a hot set of wheels and not much else, but when the Wendlings unleash four doors of frenzy, you better have brought your A game.