Grizzly gun; Chevrolet Motor Div. Impala SS sedan by Mac DeMere (Motor Trend 10/94)




   TECH DATA



   Chevrolet 502 Impala SS



   GENERAL/POWERTRAIN



   Bodystyle 4-door, 5-passenger Vehicle configuration Front

engine, rear drive Engine configuration 90 degrees V-8, OHV, 2

valves/cylinder Engine displacement, ci/cc 501/8214 Horsepower,

hp at rpm, SAE net 385 @ 5200 rpm Torque, lb-ft @ rpm, SAE net

460 @ 3500 rpm Transmission 4-speed automatic Axle ratio 3:42:1

Dimensions Wheelbase, in/mm 115.9/2445 Length, in/mm 214.1/5438

Curb weight, lb 4400 Fuel capacity, gal 23.0 Mileage (observed)

12.9



   CHASSIS



   Suspension, f/r Upper and lower control arms/ live axle

Steering Recirculating ball, power assist Brakes, f/r Vented

discs/vented discs, ABS Wheels, f/r, in 17 x 8.5, cast aluminum

Tires, f/r Goodyear Eagle GS-C, 255/45ZR17//285/40ZR17

Acceleration, 0-60 sec 6.0 Quarter mile, sec/mph 14.5/98.2

Braking, 60-0, ft130 Slalom, 600-ft, mph 61.9 Skidpad, 200-ft,

lateral g 0.80



   PRICE



   Price as tested Not for sale



   STUFFING A BIG-BLOCK INTO AN IMPALA SS



   For his deer rifle, my uncle sometimes selected a .375 H&H

Magnum, a cartridge more often chosen for dangerous game. With

recoil like a Mike Tyson punch, that grizzly gun required his

supreme marksmanship to avoid bony venison sausage. It didn't

kill the scrawny east Arkansas whitetails any deader, but he

didn't have to do much tracking. 



   Such an excessive weapon selection pales in comparison with

swapping the Impala SS' 260-horsepower 5.7-liter small-block LT1

for a 385-horsepower, 8.2-liter big-block. The result is like

equipping a deer stand with a M61A1 Vulcan 20mm cannon: It's

entertaining to have so much firepower at your fingertips, but

you can get as good or better overall results with much less.



   Mainly as an entertaining exercise, but also to evoke memories

of previous Impalas, General Motors' Motorsports Technology Group

shoe-horned a big-block "crate motor" into an early prototype of

the new generation Impala SS. (The Impala SS, in turn, is

essentially a Caprice Classic with an LT1 replacing its previous

180-horsepower V-8.) Called the H.O. 502 by Chevrolet, though the

actual displacement rounds down to 501 cubic-inches, the engine

shares the Gen V iron block with the more familiar 454, but has

0.196-inch larger bores. It's one of several such preassembled

engines offered by GM Performance Parts Division. (Ask your local

Chevy dealer for part number 10185085.) Packing a gross rating of

440 peak horsepower and a Everest-topping 514 pound-feet of

torque in single-carburetor "crate" form, this big-block is often

used in marine applications (which means boats, but it sure would

make one fast amphibious assault vehicle, too). The engine can

also legally be used as a replacement for worn-out big-blocks in

unregulated, pre-emissions-control cars, like the original Impala

SS396.



   In this exercise, the engine gets tunnel port fuel injection,

a '94 Corvette air-flow meter, and exhaust manifolds from the '84

C/K pickup parts bin. Impala SS catalytic converters are

retained, and low back pressure mufflers are added. Slap on

accessory drives, and Chevy estimates the horsepower peak falls

to 385 at 5200 rpm, with 460 pound-feet at 3500.



   Even with this "meager" output, you can spin the tires all the

way through first gear, then through the one-two upshift, and to

just shy of the two-three upshift. You'll leave two giant black

marks thanks to the Auburn limited-slip diff. Even if you launch

softly but go to wide-open throttle, the tires spin at the

one-two; with any cornering load, you get sideways instantly.

While rolling along in third gear at 30 mph, kick the loud pedal,

and it downshifts to first and spins the tires. We've never

driven a car that's easier to keep in power oversteer. Goodyear

should give away 502 Impalas like shaving-blade companies once

passed out free razor handles: We'd have to buy a set of GS-Cs

every week.



   Despite such parking-lot-donut-championship-level wheel-spin,

the 502 Impala SS streaked from 0-60 mph in 6.0 seconds and

covered the quarter mile in 14.5 seconds going 98.2 mph. That

beats a stock Impala SS' 0-60-mph time by 1.1 seconds and its

quarter-mile time by 0.9 second. Chevy claims that on a cool, dry

evening, with a tacky start line, the 502 Impala can break 14.0

in the quarter. But acceleration is the only performance

parameter in which the big-block Impala beat its small-block

sibling.



   Attacking a curvy back road with the 502 Impala is like dog

fighting with a B-52H: Entertaining, but harrowing. Both the

Stratofortress and 502 Impala perform better in straight and

level missions. With a ton and a quarter on the front tires and

enough torque to at the rear tires to uproot West Virginia, we

had a hard time finding the sweet spot between terminal

understeer and terminal oversteer. Dull steering, unsupportive

seats, and a suspension unchanged from stock Impala SS didn't

help. Despite Corvette-issue Goodyear Eagle GS-Cs (255/45ZR17

front, 285/40ZR17 rear), the 502 Impala fell far behind the stock

Impala SS (shod all-around in 255/50ZR17 all-season BFGoodrich

Comp T/A ZR4s) in skidpad cornering (0.80 g versus 0.83 g), on

the slalom (61.9 mph versus 62.9 mph), and in 60-0-mph stopping

distance (130 feet versus 120 feet). The 502 Impala couldn't even

equal the skidpad mark of the Caprice Classic, and only by

insignificant margins did it beat its parent's slalom and braking

performance. Adding 131 pounds to the front wheels obviously

isn't the way to make an Impala handle better.



   We're told that, driven sedately, the big-block is

transparent, save for a loudly burbling exhaust and 13-mpg fuel

economy. We personally would have no way of knowing, however,

since we never drove it sedately.



   Despite its high entertainment value, the 502 Impala SS gets

low marks in practicality and environmental friendliness, so it's

extremely unlikely that it'll reach production. Unless General

Motors' upper management plans an automotive deer hunt in east

Arkansas, that is.



    RELATED ARTICLE: CHEVY S-10 V-8: A CORVETTE WITH A CARGO BED



   The speed-crazed engineers at Chevrolet coyly call it "Baby

Thunder," a Corvette-powered, all-wheel-drive, specially modified

'93 S-10 pickup.



   Mark McPhail is the corporate hot-rodder responsible for this

half-ton-haulin' Mustang eater, painted Corvette Torch Red for no

attempt at subtlety. The powerplant is a 5.7-liter Corvette LT1,

squeezed into the tiny engine bay with carbon-fiber shoehorns.

Retaining functional air conditioning and ABS was an added chore,

and virtually every mechanical component on the truck has

received some sort of special attention.



   The 300-horsepower engine uses a modified oil pan with

4.3-liter V-6 4WD sump, a remote mounted oil filter, '88 Camaro

exhaust manifolds, '93 Camaro engine computer, a '94 Camaro AIR

pump, and a '94 Chevy 454 truck catalyst with dual

low-restriction mufflers. To keep the explosive 340 pound-feet of

torque from turning the little S-10 into a tire-smoking whirligig

of death, McPhail and crew installed all-wheel-drive. The

components include a viscous transfer case pirated from a Chevy

Astro Van, an S-10 four-wheel-drive front axle, and a 4L60

four-speed automatic transmission. Front and rear gearing is

3.42:1.



   Sitting a couple of inches lower at the rear, outfitted with a

'92 Camaro Z28 steering box and wearing Corvette wheels shod with

Goodyear GS-C radials (255/45ZR17 front; 285/40ZR17 rear) this

pickup also handles like no other S-10. The all-wheel-drive

system delivers quick turn-in, excellent balance, and a

jaw-dropping 66.4-mph slalom speed. That's 4.2 mph better than a

Ford Lightning and qualifies this S-10 as the fastest pickup to

ever weave through our 600-foot maze. However, its 0.80-g skidpad

orbit was less impressive, due to front-end heft that overwhelmed

the outside front tire's ability to retain tread.



   Then came the real fun. With its instant blast of torque and

epoxy-like traction, the 3456-pound pickup leaps off the line

like a Pro Stocker, auto-shifting at 6000 rpm with enough force

to cause spinal injury and marauding to 60 mph in 5.7 seconds and

past the quarter mile in 14.3 seconds at 94.3 mph. That puts you

neck-and-neck with new Z28s and an but the best of Corvettes.

Braking to a stop from 60 mph took 133 feet.



   Little added touches like a console-mounted Corvette shifter

and Pontiac Sunbird gauge cluster make this one-off pickup even

more special. However, the grim reality remains that anything

this fun would be far too costly to put into production. - C. Van

Tune