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Pro Modified, also known as Pro Mod, is a class or division in the sport of drag racing used in the NHRA (quarter-mile) and the American Drag Racing League (eighth-mile). It is similar to the Top Doorslammer class as defined by the ANDRA.
This division has specific rules about engines, components, bodies, etc. Pro Modifieds can either be raced on 1/4 mile or 1/8 mile tracks. Usually, the NHRA races Pro Mod cars on the 1/4 mile, resulting in high 5 to low 6 second passes, while the ADRL (American Drag Racing League) races strictly on 1/8 mile track setups, allowing for high 3 second-to low 4 second passes. Pro Modified has only been around for about 15 years, whereas other classes are much older. Despite Pro Modified cars being slower than the Top Fuel or Funny Car classes, it has become one of the most popular divisions of the sport. The Pro Modified division was a spin-off of the IHRA's Top Sportsman division but with fewer limitations, allowing for significantly higher performance. The American Drag Racing League's top three classes (Pro Extreme, Pro Nitrous, and Extreme 10.5) comprise Pro Modified vehicles, making the ADRL one of the fastest growing and most popular drag racing organizations. However, many adamant purists say that true drag racing should be 1/4 mile and shun the ADRL despite the free entry to races for fans. Due to the near-limitless engine/drivetrain combinations and incredibly lenient rule system used by most Pro Modified racing organizations, competing teams in this series of drag racing have virtually every freedom to make their car as fast and competitive as it can possibly be. Pro Mod has a rich history despite only being 20 years old, but the off season between the 2009 and 2010 seasons was the most controversial in years. The IHRA, known as the originators of the class, dropped the class in a move to focus more on nitromethane powered vehicles. Picking up where the IHRA left off, the NHRA announced that through a partnership with Get Screened America, Pro Mod would become a full fledged professional class, running a limited schedule but still competing for national event trophies and a world champion.
The winningest drivers in Pro Modified history are Scotty Cannon, Mike Janis and Shannon Jenkins.
There are 4 different engine combinations available for the Pro Modified category. A car utilizing a supercharger as its power adder is limited to 526 cubic inches and must have a minimum weight of 2,650 lbs with the driver. Cars utilizing turbochargers as a power adder are limited to 540 cubic inches with the turbochargers having a maximum size of 88 millimeters each. They too must adhere to the same 2,650 lb minimum weight with driver as the supercharged vehicles. Currently vehicles using nitrous oxide have no cubic inch limit but must weigh 2,425 lbs with the driver. Both nitrous and turbocharged cars use high octane racing gasoline as fuel while supercharged cars use methanol as a fuel.
These engines put out an extremely large amount of horsepower, some at approximately 2500 to upwards of 4000 H.P. The engines propel the cars down the track at speeds of over 250 mph. Most supercharged engines are based on Chrysler's 426 Hemi engine. The exhaust system is similar to that of a Funny Car. Simple short header pipes bolted onto the engine block heads extend down from the motor and curve upward just before reaching the ground. The exhaust pipes are visible just behind the front wheels of the vehicle. Most of the time, each exhaust port on the heads has its own individual pipe, but occasionally the four pipes on each side of the engine block converge into one single header collector on each side of the motor, resulting in two exhaust pipes instead of eight.
The body of a Pro Modified car is somewhat similar to a Pro Stock race car, yet also radically different at the same time. Whereas Pro Stock cars retain street identification, Pro Modified cars' bodies are just that: modified. Pro Mod race cars have either a forward-facing (with the opening in front) hood scoop for nitrous injected cars, or the hood may be cut to allow a supercharger to be fitted through onto a blown motor. Also, a Pro Modified car is usually fitted with a long, flat wing extending from the base of the rear windshield and past where the lip of the trunk lid would be on a normal car. This wing aids in downforce and stability, and helps keep the car on the ground. Many body styles are represented in the Pro Mod class. Everything from a Plymouth Superbird to a Volkswagen Beetle has been seen at the dragstrip in Pro Mod fitting. Some of the more common body styles include the Chevrolet Corvette and Camaro, the Ford Mustang, and Studebaker vehicles. Small pick-up trucks, like the Chevrolet S-10 also make for popular Pro Mod vehicle choices. The material with which the body of a Pro Modified race car is constructed out of is a Carbon Fiber or similar composites, similar to the material used in the bodies of most race cars. In 2008, the IHRA banned any body style of a current legal Pro Stock car (Chevrolet Cobalt, Dodge Stratus, or Ford Mustang, Holden Commodore, or the former Pontiac G6 GXP) from being used in Pro Modified, but that rule disappeared when the IHRA ceased sanction of the class. Any legal body style is permitted in NHRA or ADRL sanctioned races, with former NHRA Pro Stock Motorcycle champion Matt Smith racing his father's (Trickie Rickie Smith's) 2010-style Chevrolet Camaro at the 2011 U. S. Nationals.
A Pro Modified car may have anywhere from a 2-speed transmission (more commonly used on 1/8 mile tracks) to a 5-speed transmission (used mostly on 1/4 mile tracks). An automatic transmission or a manual transmission may be used with any combination of rear-end gears.