Pro Stock
From Wikipedia, the free encyclopedia
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.
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[edit] History
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 favoured big-block V8s but by 1972 had changed to favour small-blocks to reflect contemporary trends in the American auto industry. 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.
[edit] Pro Stock today
[edit] Engine
- 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.
- If the car is a General Motors car (Chevrolet Cobalt or Pontiac G6 GXP), the block must be from any General Motors division. In General Motors' case, a factory Drag Racing Competition Engine, based on the current Vortec 8100 engine, is used.
- Engine capacity is restricted to a maximum 500 in³ (approx 8.2 L) single-camshaft, 90-degree V-8.
- Some non-NHRA bodies will have different rules. Live Nation's IHRA does not have a 500-cubic inch rule, and some engines exceed 800+ in³, known as "mountain motors."
- Pro stocks are limited to carburetor (naturally aspirated) intake systems, however 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 predicate the large hood scoop that is a signature of the Pro Stock class.
This has resulted in Pro Stock heads being the most sophisticated in any drag racing category.
Pro Stock engines generally produce around 2.5 hp/in³ (114 kW/L). A complete Pro Stock engine normally costs more than $80,000.
[edit] Drivetrain
- 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 IHRA Pro Stock and in Air-Shifted three-speed units in IHRA Pro Modified, NHRA Pro Stocks utilize a Liberty or G-Force five-speed clutchless manual transmission.
[edit] Suspension
- 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 the four-link.
- Coil- over shock absorbers are used at both front and rear.
[edit] Brakes
- Four-wheel disc brakes made by aftermarket manufacturers are used in conjunction with dual parachutes to slow Pro Stockers after near 200 mph (320 km/h) runs.
- The brakes have single calipers on the front and double calipers on the rear.
[edit] Fuel
- The factory hot rods may use only racing gasoline (octane rating: 118), which is tested and certified by chemical analysis at NHRA[1] or IHRA events.
- Pro Stock fuel systems flow the gasoline at 7.5 US gallons per minute (0.5 L/s).
On top of all of these specifications, each car must:
- Weigh a minimum of 2,350 pounds (1066 kg), including driver.
- In NHRA competition, the cars must be 2003 model or later cars. In the late 1980s and into the 1990s, car sizes increased as mid-size family sedans had become the car of choice; today, many NHRA cars are mostly based on out-of-production mid-size cars (Dodge Stratus, with some teams running the Pontiac GTO). General Motors factory teams will race in 2008 with current cars in production, as Chevrolet teams race the Cobalt, as they have since 2005 (the first year of the Cobalt), and Pontiac teams will move to G6 GXP.
- 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 original factory location.
This makes for some incredibly tight racing; the front runners in the class can reach speeds over 200 mph (320 km/h) in 6.6 seconds (approx). The qualifications rounds are only 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.
IHRA Pro Stock cars, because of their 800+ cubic inch mountain motors, dip into the 6.30's at almost 220 miles per hour. Recently, a few cars have dipped into the 6.20's, with Brian Gahm being the first with a 6.29 second pass at Grand Bend Motorplex.
