Aside from a fast car, the one thing you need to set land speed records is space. Across California, Nevada and Utah are the dry beds of giant prehistoric lakes. These salty, wide-open expanses are flat and smooth. In other words, they're perfect for top-speed runs, which is why hot rodders have been using them since the 1930s. Today's cars have gone over 600 miles per hour (966 kilometers per hour) on the Bonneville salt flats, a rock-hard lake bed in Utah that's synonymous with speed trials and fast cars [sources: Christensen; Wise].
To set an official record, during the official Speed Week at Bonneville, for example, each car is given two runs through the course. The average speed from those two runs is used to determine the final speed for the car [source: Wise].
One of the most famous belly tank racers is associated with Alex Xydias and his iconic So-Cal Speed shop. Built from the belly tank of a P-38 Lightning and powered by a 156-cubic inch (396-cubic centimeter) V-8, the So-Cal Speed Shop belly racer ran at an average speed of 145 miles per hour (233 kilometers per hour) at Bonneville in 1951. Later, So-Cal swapped out the engine for a larger one and averaged 181 miles per hour (291 kilometers per hour) with the new rig. They swapped the engine out yet again (because if it worked once, why not try it again?) and managed to average 195 miles per hour (314 kilometers per hour) [source: Barracuda Magazine].
Other classic belly racers include the one from Mal Hoopster, which broke the So-Cal Speed Shop record with a Chrysler-powered belly tank racer that averaged 197 miles per hour (317 kilometers per hour). Bill Burke, a hot rodder who worked at So-Cal Speed Shop and is widely credited with first noticing that belly tanks would make great race cars, built a belly tank racer that made it up to 131 miles per hour (211 kilometers per hour) [source: Barracuda Magazine].
A classic belly tank racer from the 1940s and 50s would be expensive to buy today, so you're not likely to see them at the racetrack. The So-Cal belly racer that made it up to 195 miles per hour (314 kilometers per hour) is worth nearly $200,000 today [source: Wilkinson]. But if you don't have that kind of cash to spare, you can always head out to Speed Week at Bonneville in August and see the heirs of the belly tank racer's legacy hit speeds the original models could only dream of.