Some months ago we introduced you to our in-house '96 Chevy Caprice 9C1, better known as a cop car. This specimen of the last fullsize rear wheel drive Chevy is equipped with the vaunted Gen II LT1 engine, displacing 5.7 liters and rated at 260 hp with iron cylinder heads. Our interest in the car was primarily as an urban commuter, battling its way through the mean streets of LA while providing a degree of comfort and utility, along with their well-known durability. We selected an LT1 Caprice specifically because of the impressive performance these cars deliver, and since mechanically the 9C1 is nearly identical to the Impala SS of the same era, aftermarket support is available to make it even better.
The time lapse between our introduction of the car and now was due primarily to an extended "shakedown" period, which shook out a steady stream of maladies. Since our car had 175,000 miles when purchased (the engine was replaced with a GM service long-block at 106,000, as was the trans), niggling problems like leaky coolant hoses, burned-out fan relays, and fried ignition parts are expected. But now that the car has provided about 10,000 miles of relatively trouble-free motoring, it's time to turn up the heat.
For the initial thrashing, we strapped our retiree to the Superflow chassis dyno at Westech Performance Group in Mira Loma, California. Rather than throwing a pile of go-fast parts at the high-mileage cruiser, we opted instead for simple tweaks to monitor the car's reaction to ensure the old enforcer is up to the task. If the car responds favorably to the basics, we'll take it as an indication that it's safe to venture on to more serious hardware.
We wanted to make sure the Caprice's lubricants and filters were up to snuff prior to hitting the dyno, to ensure that we weren't introducing other variables into the equation. Besides, the dyno can give a car a real workout, so having fresh fluids is always a good idea. To begin, we used standard Valvoline 5W30 (factory spec) along with a K&N oil filter. The fuel filter was also replaced with a Fram service replacement part.
The ignition parts on our Chevy were also well worn, so we swapped in a fresh set of stock-spec AC plugs and a set of MSD plug wires. The wires for the LT1 are somewhat unusual since all Gen II small-blocks use the Opti-Spark ignition system, which is based in a distributor mounted behind the water pump. The task of changing these wires looks deceptively simple, but is actually a major chore, since the wires are routed behind the front accessory drive components and behind the exhaust manifolds in steel looms. It's worth doing on high-mileage cars, though, since this routing allows the engine's heat to take its toll on the LT1's ignition wires.
This being the first trip to the rollers for the Caprice, we wanted to establish a solid baseline. The first pulls were made as the car came off the street--210-degree coolant, 91-octane fuel, and with all factory air intake and exhaust pieces in place. The Caprice has an excellent cooling system, but the factory programmed the electric fans to stay off until the coolant reaches nearly 225 degrees to keep idle emissions clean. This is reflected in the temp gauge as the needle reaches just shy of the three-quarters mark. When the needle sweeps past the straight-up point (typical for non-highway driving), performance falls off substantially judging by seat-of-the-pants input. Our first pulls were made at around 210 degrees, and showed 217 hp and 276 lb-ft.
There are several means of activating the cooling fans at lower temps, including computer reflashing and aftermarket programmer devices. Both are effective, but we decided to take a more mechanical approach by using one of Jet Performance's fan controller switches. The switch comes with wiring to tap into the factory harness and triggers the fans at a lower temp, which in turn allows the engine to run closer to the temp dictated by the thermostat, in this case around 195 degrees. This simple change bumped power up to 222 while torque climbed to 280 lb-ft.