9C1 is Chevrolet's Special Equipment Options (SEO) code for a police package vehicle. The 9C1 package has heavier-duty (HD) features over a non-police vehicle as well as some options specific to the installation of police equipment. The Chevrolet Nova, Malibu, Caprice, Impala, Tahoe, and Camaro have all been available with Police Package options. Some of the models are designated by different SEO codes, such as B4C for the Camaro Police vehicle.
HD features include full perimeter steel frame (there is debate as to whether the 9C1 Caprice uses a thicker frame than the civilian car; GM replacement frame part numbers for the civilian auto and the 9C1 Caprice are the same); oversized front and rear sway bars; full-size spare tire (in the case of the last-generation 1994-96 Caprice Classic police car); high-output alternator; lifetime-rated green silicone coolant hoses; four-wheel disc brakes; HD steel wheels and speed-rated tires; separate engine, power steering and transmission oil coolers; certified digital speedometer; stiffer body mounts and more of them; true dual exhaust; anti-stab steel plates in the front seat backs; performance 3.08 final drive ratio (3.23 w/std. 200 hp/245 ft·lbf L99 V8 4.3 L (265 cid) SFI engine); and extra wiring for the emergency equipment. The 260 hp/330 ft·lbf cast iron head, sequential multiport fuel injection, reverse-cooled, Corvette-derived LT1 5.7 L (350 cid) V8 was a popular option for these final years and helped make the '94-'96 9C1 Chevrolet Caprice Classic one of the fastest and best-regarded police cars in US history.
9C1 is also the code for "police pack" Holden Commodores in Australia, which can be equipped with the 5.7 litre Chevrolet engine, that made the 9C1 so popular and has been touted as a possible Successor to replace the Crown Victoria in police fleets.