There's no question that cop cars get abused. Just think back about their on-screen counterparts depticted in television shows such as Baretta, Starsky & Hutch, and Nash Bridges, to name just a few. With so much time on the clock and with the stress of high-speed chases and day-to-day cruising, it's hard not to imagine anything other than the boneyard for most retired cruisers.
Not quite. In fact, most police patrol (and undercover) vehicles find a second life in the hands of civilians after their pursuit careers are over. And in the case of this Caprice, its resurrection was in the hands of a performance-oriented police officer who, in addition to his love of the Impala and Caprice models, just didn't want this low-mileage car to find a home in any one else's garage but his.
The limited-production Impala SS, with its blending of heavy metal and high performance, has spawned a dedicated group of enthusiasts, whether owners or dreamers. But the escalating selling costs of used Impalas has frustrated many enthusiasts, turning their attention toward the next likely candidate, the 9C1 Law Enforcement Package Caprice. This vehicle has less amenities, but offers the same basic body shell, chassis, and LT1-based powertrain as the SS Impala. In fact, owners of 9C1Caprices are able to brag about their additional power steering fluid coolers as well as the greenish-colored high-temperature-silicon water system hose.
The same type of performance upgrades that are popular on the Impala were bestowed upon "Coprice," the vehicle featured here. The owner of the 9C1 package that was used for this transformation project was fortunate to have purchased the car from an ex-reserve New Mexico State Trooper turned military-serviceman. The trooper, who was the original owner, was able to order his own law enforcement package vehicle through a fleet buying program. Due to his part-time status, the '96 Caprice was used in service for a minimal amount of time, and pampered like no other car in the agency. Unfortunately, the car had to be sold because the original owner was "shipping out" overseas to serve our country.
Enter the new owner, who drooled at the sight of a clean Impala SS. His budget did not allow for an Impala, but this unusually clean Caprice would work just fine for a full aftermarket renovation. Now we would embark on our high-performance make over. Typically, when a barrage of performance items are changed on a vehicle, some areas of performance testing may actually suffer. Much to everyone's pleasant surprise, we would see improvements in every aspect during our before and after testing.
The first order of business was to take the bone stock cop car to a remote test track that could be used again for final testing. Holtville Aerodrome International Raceway, located in the southern-most tip of California, complete with 100-degree desert heat, was selected. The car was subjected to a battery of tests, including 1/4-mile acceleration, 0-60 acceleration, 60-0 panic stops, 80-0 panic stops, consecutive laps on a 1.433-mile SCCA road racing track, and finally a workout on a 200-foot diameter skid pad. The surface at this facility is abrasive concrete, but its composition would remain consistent from the time of the original baseline test to the final shootout. After grinding the stock 15-inch rubber to near baldness, we were confident with our initial test data, which cleared the way for making changes.
The first step to achieving a more powerful behemoth was to go to NOS (Nitrous Oxide Systems) in Costa Mesa, California, for a NOS EFI nitrous oxide kit. The NOS system is engineered with a failsafe mechanism utilizing dual nitrous solenoids that only allow full nitrous pressure when the OE fuel pressure "ramps up" to its maximum. Once armed, a throttle position switch activates the system when the linkage nears full throttle. Realizing this was a heavy car, it was decided to add a second 10-pound bottle in the trunk so there would be plenty of laughing gas on board for several sprints. NOS Bottle Pressure Gauges were also utilized in order to monitor the nitrous pressure in each bottle. To further ensure that the system would be at its optimum, a pair of NOS Electric Bottle Heaters along with a pair of NOS Bottle Blankets was also added.
During test launches with the nitrous-tweaked OE chassis, it was immediately obvious that the car required suspension work before continuing with the engine upgrades. The tail of the big boat would track off-center as the factory suspension links flexed. Hotchkis Performance upper and lower boxed trailing arms were installed on the rear axle to keep it in line. Although the stock handling on the road racing track proved impressive for such a large ride, its suspension height was designed for "hopping curbs" while pursuing the criminal element. H & R Special Springs replaced the OE coils, lowering this police package by roughly 3 inches while properly leveling the car on all four corners. Normally, an Impala SS would be lowered by only 2 inches, but this "cop edition" sat high. Tokico HP high-pressure, twin-tube gas shocks were installed on each corner. Hellwig Suspension Products "Sport Tech" anti-sway bars replaced the front and rear factory items, increasing the bar diameter enough to improve the roll stiffness and tame this heavy chassis. All of the suspension components, as well as the second nitrous bottle, were installed at Michelangelo Motor Werkes in Irvine, California.
During the baseline testing, the 4,500-pound Caprice performed reasonably well during the braking tests. However, once the braking system was subjected to repeated use on the road course, the weight, along with the unventilated rotors, was apparent. While entering Holtville's Turn 5 during the third lap, which required heavy braking from 100 mph, the pads failed. The car used the entire turn, including some agricultural driving, in order to keep the shiny side facing the sun. After that thrill ride, we contacted Power Performance Group in Chatsworth, California, which specializes in brake system upgrades. They recommended a set of Power Slot Police Package Brake Rotors. During the installation, the owner of the Caprice elected to switch to Raybestos carbon-metallic brake pads in order to further help the braking performance. All of these improvements in suspension and braking will only work to the limitations of the rubber on the car. The owner loved the look of the factory 17-inch Impala SS wheels and felt that the wheel diameter would best suit his driving, but he also desired a larger contact patch than what is available on the stock Impala. An extensive search revealed that it is difficult to locate a proper wheel fitment for these cars because they feature a 5x5 bolt circle, similar to that found on late-model GM trucks. Unless you wish to install Gumbo Monster Mudders, or go to the expense of custom three-piece wheels, your options are limited. Group A Autotrend in Phoenix, distributor for Australian made ROH Wheels, had a solution-their one-piece ZR6 cast aluminum wheels, which feature similar styling to the factory Impala SS, but feature a 17 X 9-inch size in the correct offset to allow for massive 285-series rubber (the stock Impala is 255 series). Pirelli manufactures the P-Zero performance radial tire in a 285/40ZR17 size, fitting perfectly on this chassis. Its special tread design is unidirectional for optimum handling in both wet and dry, and delivers good wear characteristics for their level of adhesion. In fact, the Pirellis showed less wear during the abusive track testing than the harder, stock 225/70-15 police car tires.
With a desire for his car to develop additional horsepower, even when the NOS system was not being engaged, the engine's breathing capacity on both the inlet and outlet sides of the cylinder heads were upgraded with a K & N Filtercharger air filtration system. The inlet tube diameter is larger, while the high-flow cotton gauze element resides in its own partitioned fresh-air box, which is supplied with the kit. The upgraded exhaust system consists of a Borla T-304 aircraft-grade stainless steel Cat-BackTM system, and an intricate set of T-304 stainless steel headers. The headers carry a California Exemption Order number and complement the high-performance exhaust system. Besides adding to the looks and performance of the LT1-powered car, the sound is vastly improved over theOE system, which "chuffed" through a drain hole in a muffler during operation.
In order to accomplish the acceleration desired for the Caprice, the factory rearend ratio was replaced with a 3.73:1 ring-and-pinion. A Hypertech Power Programmer III engine management and shift programmer was installed, which includes program functions to compensate for the speedometer error. The Power Programmer III further improves the vehicle's performance, and was purchased along with a 160-degree "PowerStat." With a simple manipulation of the factory GM software accomplished by following Hypertech's instructions, the speedometer was corrected for changes in both the tire diameter and gear ratio. During the process, the shift pressures were modified for a firmer shift, while the shift points were also calibrated along with the rev limit in each gear. The Power Programmer III allowed us to experiment with shift and rpm calibration at the race track. Changes to the program were made in between runs, taking roughly 10 minutes each time.
Finally, after nearly a year of assembling the project, the Caprice was taken back to Holtville for its final performance evaluation. As shown in the testing chart, the performance for the big car excelled in virtually every test, whether accelerating, stopping, turning in a circle, or blasting around a race track. We are certain that the acceleration numbers would have been even quicker if we had less air pressure in the tires, or installed a set of street slicks. The air pressures were set deliberately high in order to conform to the previous testing parameters that were designed to prevent the tire walls from rolling onto their sides. The most notable characteristics, which were not shown in the test figures, included a major improvement in straight-line stability along with far less chassis roll in the corners. Originally, the heavy car would keel over to one side, then remain relatively neutral during a long corner. The combination of the suspension tweaks and big Pirellis made the car more prone to a slight oversteer condition that was corrected with small inputs in the steering. The lower profile tires combined with oversteer made the car feel more nervous, but boy was it faster! As in more than three seconds a lap faster without using nitrous. In fact, the times were faster than some of the lightweight racing sedans that compete in the Improved Touring classes of SCCA. Lights, siren, bullhorn...action!
There was one casualty during the test, its demise most likely hastened by our rapid steering inputs. The factory power steering pump rolled over and played dead on the last lap of the road course. Typically, the car was tested in three-lap dashes, then allowed to cool down. The driver neglected to properly count the laps during the last segment and ran an additional lap. At almost the same moment that the power steering pump failed, the stock DOT 3 brake fluid boiled, caused by shear overheating and overuse. This was not caused by the upgraded brake components, however, because they survived the three-lap dash far better than the previous "agricultural racer." If anything, the sticky Pirelli P-Zero tires saved our tail this time by allowing the thundering monster to make the harrowing turn with very little braking and steering. With the skid pad being the last test on the agenda, it proved a more laborious task to keep the car in a crisp circle, potentially hurting our final numbers. The inability to balance the car on the limit with a rapid steering input may have cost us a few tenths of a second during the timed circles.
Ultimately, we left the test satisfied that we reached our goal of improving the big car's performance throughout its entire range. This would hold true, whether making a trip to the drag strip, running the big sled through the twisties, or making a panic stop. The ride is more firm, but enjoyable, while the sound of the car has improved immensely. All of these upgrades were accomplished for less than the cost of a used Impala. Of course, any Impala owner would be glad to have these additions to his or her machine.
Location: Holtville Aerodrome International Raceway. Testing equipment included a Vericom VC200 for acceleration and braking, and timing equipment for the measured skidpad and 1.433-mile road course.
Ambient temperature during both tests: 100 degrees F.
Final Performance Test: 7/27/99
|1/4-MILE ACCELERATION |
|Baseline ||Final || |
| ||(W/O NOS) ||(WITH NOS) |
|Best e.t.: 16.36 sec. ||15.22 sec. ||14.25 sec. |
|Best Speed: 88.3 mph ||94.1 mph ||103.0 mph |
|Average: 16.42 ||15.40 ||14.28 |
|@ 88 mph ||@ 93.4 mph ||@ 101.3 mph |
|0-60 ACCELERATION |
| ||Baseline ||Final |
|Best: 8.47 sec. ||7.37 sec. ||6.64 sec. |
|Average: 8.48 sec. ||7.38 sec. ||6.79 sec. |
|60-0 BRAKE TEST (FULL ABS) |
| ||Baseline ||Final |
|Best: ||119 feet ||110 feet |
|Average: ||123.5 feet ||110.5 feet |
|80-0 BRAKE TEST (FULL ABS) |
| ||Baseline ||Final |
|Best: ||225 feet ||204 feet |
|Average: ||226.5 feet ||207.5 feet |
|200-FOOT SKID PAD |
| ||Baseline ||Final |
|Best: ||.64g ||.80g* |
|Average: ||.63g ||.77g* |
|* Final testing performed with failed power steering pump. |
|1.433-MILE ROAD COURSE |
| ||Baseline ||Final |
|Best: ||1:16.37 ||1:13.12 |
|Average: ||1:16.90 ||1:13.20 |
Borla Performance Industries
5901 Edison Dr.
K & N Engineering, Inc.
P.O. Box 1329
Group A Autotrend
251 E. Chilton Drive
Michelangelo Motor Werkes
15801 Rockfield, Unit P
Hellwig Suspension Products
16237 Avenue 296
Nitrous Oxide Systems, Inc.
2970 Airway Ave.
12035 Burke St., Ste. 13
Santa Fe Springs
H & R Special Springs
3815 Bakerview Spur #7
Power Performance Group Inc.
9001 Oso Avenue, Unit A
1910 Thomas Rd.
Tokico (USA) Inc.
1330 Storm Parkway