Buick's Century is one of its most storied offerings; the name and design premise dates back to the Great Depression. Although the Century was replaced by Buick's brand new LaCrosse in 2005, the car still remains popular for those seeking comfort and luxury at an entry-level price. Although performance engine offerings for the Century are pretty thin--it came only with General Motor's base-model 3100 V6--the car does have one thing going for it; under the skin, Century is mechanically identical to its Monte Carlo and Impala cousins.
You're pretty much out of luck when it comes to bolt-on performance goodies for the 3100. If working on a 1999-or-earlier car, installing an intake manifold from a 2000-or-later 3100 adds approximately 10 horsepower. Vehicle limitations include universal bolt-ons, such as cold air intakes and converter-back exhaust systems designed for 3.1-liter Monte Carlos and Regals and custom machine work, such as cylinder head porting and custom parts, like fabricated exhaust headers.
Purchase an under-drive pulley set for this motor to slow the alternator and water pump down, which may be worth as much as another 10 horsepower. Extrude hone stock intake and exhaust manifolds by using a qualified machine shop. This process involves blasting an abrasive through air passages to increase size and flow more air.
Supercharging an engine with absolutely zero aftermarket support is no small feat, but it can be done. This engine has two things going for it where forced induction is concerned: an acceptable compression ratio of 9.5 to one and a mass airflow fuel injection system, which is far more adaptable to turbo or supercharging than the manifold air pressure systems used on other cars. The only exceptions are the 1995 and some 1996 models, which still use manifold air pressure systems. Safely run about five to seven pounds per square inch of boost without any changes to the computer tuning or engine, which would be good for about 240 to 270 horsepower in this application--about 30 less for supercharging.
Space is tight in the Century's engine bay, so engineer a low-mount centrifugal supercharger set-up or go with a rear-mount turbo in place of the factory muffler. Either way, this requires advanced skills with a welder and between $2,000 for the rear-mount turbo setup and $4,000 for the supercharger to get there. Start with a universal-fit turbo or supercharger from a manufacturer like Vortech, Paxton or Mitsubishi and build the system out from there.
Things become easy with the chassis. Impala and Monte Carlo have plenty of aftermarket supports for the brakes and suspension. Purchase a big brake kit, rotors, new calipers or pads and braided steel brake lines from Brembo, Stoptech or Rotora.
Coil-over suspension kits, which include performance struts and lowering springs, stiffer anti-roll bars and other suspension pieces, are available from Bilstein, Koni and KW suspension. To tighten up the Century's suspension response at the expense of some ride comfort, look into a set of polyurethane suspension bushings from Energy Suspension or Hotchkiss.
