Lightweight things move faster than heavier things -- that's as basic as physics can get. This solution is simultaneously low-tech and work intensive, in that it involves switching out heavier parts of the car (throughout the car, not just in the engine block) with lighter parts so as to make the car lighter and more aerodynamic. There are a lot of options: get rid of extra seats you don't use if you don't cart a lot of people around; replace glass windows with lighter plastic or acrylic versions; or even remove parts of the dashboard. Disc brakes even offer significant weight difference over traditional brakes.
For lots more information on engine performance, see the links on the next page.