Pro Stock Drag Racing is a class of drag racing featuring 'Factory Hot-Rods'. The class can be known as "all motor", as the cars cannot use artificial induction such as turbocharging, supercharging or nitrous oxide, and there are very strict rules governing the modifications allowed to the engines and the types of bodies used.
The National Hot Rod Association Pro Stock class emerged from the production-based Super Stock class in 1970 with a more liberal set of rules and an absence of handicaps. Rules initially favored big-block V8s but by 1972 (after the Sox & Martin Hemi cars captured the first two prostock titles handily) had changed to favor small-blocks to factor out the Chrysler Hemi cars. In 1982, the NHRA implemented a new engine formula that allowed the big-blocks to return, due to the popularity of the Mountain Motor IHRA Pro Stocks with unlimited displacement in the late 1970s. However, NHRA still limits the size of the engine to no more than 500 cubic inches(about 8,194 cubic centimetres) in displacement.
Pro Stock today
- The engine must be manufactured by the same company as the car body. Though no engine currently being raced in Pro Stock is used on any manufacturer's assembly line, all of the raw components are available to anyone. Engine blocks and cylinder heads are often provided in a "raw" condition with only approximate dimensions and rough machining. Each team will continue to machine and modify the part to their own standards.
- NHRA Pro Stock engines are restricted to a maximum 500 cu in (8.2 L) single-camshaft, 90-degree V8.
- Some non-NHRA bodies will have different rules. The PDRA (eighth-mile) and IHRA do not have a 500-cubic inch rule, and some engines exceed 800 cu in (13.1 L), known as "mountain motors."
- The Australian National Drag Racing Association has a 400 cu in (6.6 L) engine limit.
- Pro stocks are limited to dual 4-barrel carburetor (naturally aspirated) intake systems. The four-barrel carburetors can be "split" (i.e. sawn in half)(but not in NHRA Pro- Stock) so that each of the halves can be more accurately positioned over the slightly staggered intake runners. The intake manifold and heads are open to modification. The most effective intake manifold configuration has continued to be the "tunnel ram" for nearly 40 years. The carburetors are raised above the engine; the length and configuration of the intake passages ("runners") is critical to horsepower output. The tall intake manifolds necessitate the large hood scoop that is a signature of the Pro Stock class.
- Starting in 2016, NHRA will require all Pro Stock teams to equip their cars with electronically-controlled throttle body fuel injection systems.
- An electronic control unit (ECU) will be implemented on the EFI systems, including a 10,500 RPM limit.
The rules that forbid forced induction of any sort, plus allowing head modifications, have resulted in Pro Stock heads being the most sophisticated in any drag racing category, with valve lifts in the 1" region.
Pro Stock engines generally produce around 2.5 hp/in³ (114 kW/L).
A complete NHRA Pro Stock engine costs more than $250,000.
- Pro Stock clutches utilize multiple discs. These must be serviced after every run to maintain critical tolerances that can mean the difference between a good run or severe tire shake.
- Since 1973, the most popular transmission was the Lenco planetary design, first used as a four-speed and now as a five-speed. Although the five-speed unit (usually air-shifted) is still used in ADRL and Mountain Motor Pro Stock Association and in Air-Shifted three-speed units in Pro Modified, NHRA Pro Stocks utilize a Liberty or G-Force five-speed clutchless manual transmission.
- NHRA Pro Stock racers use NHRA approved carbon fiber bodies. Windows are manufactured from polycarbonate.
- Some have complained that the "Stock" portion of "Pro Stock" is not really all that accurate anymore, because so little, if any, of the race cars' bodies having their origins in the respective manufacturers' factories.
- Pro Stock chassis are welded 4130 chrome-molybdenum alloy steel tubing, with an integrated "funny-car style" cage around the driver that, combined with the safety restraints and helmet produce a very rigid and safe driving environment.
- Pro Stock cars are required to use automotive-type suspension systems.
- Since the 1970s, front suspensions have utilized MacPherson struts with control arms; for rear suspensions, the design of choice is a four-link suspension with coil over shock absorbers connected to a fixed rear axle.
- Both the front and rear shock absorbers can be adjusted automatically during the run by air circuits that are controlled by an electronical control unit.
- The primary means of slowing the cars from their top speeds of around 213 mph are the dual drag chutes.
- The chutes utilize either springs or compressed air launchers to get the chutes into the air as fast as possible and to avoid the dead air behind the car.
- Four-wheel disc brakes made by aftermarket manufacturers are also used.
- The brakes have single calipers on the front and double calipers on the rear with carbon fiber rotors.
- The factory hot rods may use only racing fuel (octane rating: 118), which is tested and certified by chemical analysis at events with the sanctioning body's approval.
- Some organisations will mandate a specification fuel. The NHRA will mandate a specification Sunoco racing fuel, but it is unknown if the specification fuel will be unleaded racing fuels as they are in other classes of motorsport where they are official fuel, or allow alcohol in the official NHRA fuel (as has been the case in INDYCAR, 85% ethanol, or NASCAR, 15% ethanol).
- Pro Stock fuel systems flow the gasoline at 7.5 US gallons per minute (0.5 L/s).
In addition to all of these specifications, each car must:
- Weigh a minimum of 2,350 pounds (1,066 kg), including driver.
- In NHRA competition, the cars must be produced within the last five model years (2011–2015). In the late 1980s and into the 1990s, car sizes increased as mid-size family sedans had become the car of choice, but cars shrank by the 2000s (decade) as compact cars, banking off the popularity then of the sport compact class, became the trend, as General Motors and Daimler (then owning the Dodge brand) began using compact cars (similar to Pro RWD except for the engine). However, that the push back to pony cars and mid-size family sedans became the choice again, as Ford uses a "pony car" and Dodge and Chevrolet began using mid-size family sedans. The 2013 legal cars are the Chevrolet Camaro, Dodge Avenger, and Ford Mustang. For 2014, Fiat teams are transitioning to the Dodge Dart.
- Rear spoilers cannot be longer than 13 inches (330 mm), measured from the body-line-to-spoiler transition point to the tip.
- Complete stock headlights, parking lights and taillights must be retained in the original factory location. This makes for some incredibly tight racing; the front runners in the class can reach speeds over 213 miles per hour (343 km/h) in 6.47 seconds (approx). The qualifications rounds are separated by less than a tenth of a second across all competitors. In a particularly tight qualifying roster, the difference from #1 to the final #16 qualifier may be only .05 seconds.
MMPSA cars, because of their 800+ cubic inch mountain motors, dip into the 6.30's at almost 220 miles per hour (354 km/h). Recently, a few cars have dipped into the 6.20s, with Brian Gahm being the first with a 6.29 second pass at Grand Bend Motorplex.
NHRA Pro Stock Champions (1974–present)
- 1974 - Bob Glidden
- 1975 - Bob Glidden
- 1976 - Larry Lombardo
- 1977 - Don Nicholson
- 1978 - Bob Glidden
- 1979 - Bob Glidden
- 1980 - Bob Glidden
- 1981 - Lee Shepherd
- 1982 - Lee Shepherd
- 1983 - Lee Shepherd
- 1984 - Lee Shepherd
- 1985 - Bob Glidden
- 1986 - Bob Glidden
- 1987 - Bob Glidden
- 1988 - Bob Glidden
- 1989 - Bob Glidden
- 1990 - Darrell Alderman
- 1991 - Darrell Alderman
- 1992 - Warren Johnson
- 1993 - Warren Johnson
- 1994 - Darrell Alderman
- 1995 - Warren Johnson
- 1996 - Jim Yates
- 1997 - Jim Yates
- 1998 - Warren Johnson
- 1999 - Warren Johnson
- 2000 - Jeg Coughlin
- 2001 - Warren Johnson
- 2002 - Jeg Coughlin
- 2003 - Greg Anderson
- 2004 - Greg Anderson
- 2005 - Greg Anderson
- 2006 - Jason Line
- 2007 - Jeg Coughlin
- 2008 - Jeg Coughlin
- 2009 - Mike Edwards
- 2010 - Greg Anderson
- 2011 - Jason Line
- 2012 - Allen Johnson
- 2013 - Jeg Coughlin
- 2014 - Erica Enders-Stevens
The most successful winning driver in Pro Stock is 10 times champion Bob Glidden. The driver with the most wins in a single season is three time champion Darrell Alderman, who won all but three events en route to his 1991 championship.
Most NHRA Pro Stock wins
- "NHRA Makes Changes To Pro Stock Class". National Speed Sport News. Turn 3 Media LLC. Retrieved 25 July 2015.
- NHRA 2010 Rule Book Amendments