The NHRA has strict guidelines for funny cars. Most of the rules relate to the engine. In short, the engines can only be V-8's at 90 degrees. (The most popular design has been the 426 Chrysler Hemi[?].) There can only be two valves per cylinder and superchargers are restricted to a basic Roots type--19 inch rotor case length with a width of 11.25 inches. The engine displacement can only be from 490-500 cubic inches. Only single camshafts[?] are allowed. There are two common bore X stroke combinations. 4.18 X 4.50 (Called a 3/4 stroker) and 4.25 X 4.38 (called a 5/8 stroker). The 3/4 stroker is the most common combination used today and equals 496 ci.
Engine blocks are usually made out of forged aluminum. Crankshafts are made from billet chrome[?]-vanadium steel. Intake valves are titanium and of 2.40-inch diameter, while exhaust valves are 1.90-inch diameter made out of Inconel[?]. Every funny car has ballistic blankets[?] covering specific parts of the engine prone to explosion.
Funny car fuel systems are key to their immense power. Most systems will deliver from 500 to 600 pounds of fuel pressure at as much as 75 gallons per minute. During a single run (Starting, burnout, backing up, staging, 1/4 mile) cars can burn as much as 15 gallons of fuel. The fuel mixture is usually 98-99% nitromethane with 1-2% alcohol. The ratio of fuel to air can be as high as 1:1. Compressions ratios vary from 6:1 to 7:1. The engines in Funny cars commonly exhibit varying piston heights and ratios that are determined by the piston's proximity to the air intake. Funny cars have a fixed gear ratio[?] of 3.20 to 1 and have a reverser[?]. Wheelbase[?] is between 100 and 125 inches. The car must maintain a 3 in ground clearance.
Various safety rules are also in place to protect the driver, spectators, and others. The most obvious requirement is a parachute to help slow the care down once it crosses the finish line.
A well-known driver in Funny Car racing is John Force[?].
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