The history of the Pro Stock class is being celebrated by NHRA in 2020 with a 50 Years of Pro Stock salute. The cars have come a long way since their debut at the 1970 Winternationals. Here's a look at the very first Pro Stock rules, as printed in the 1970 NHRA Rulebook.
PRO STOCK ELIMINATOR
Reserved for American built cars with American automobile engines with a wheelbase of 97 inches or more. Body engine, drive train, chassis, etc., may not be altered, modified or relocated, except as outlined in Class Requirements. Push starts not permitted. One class of competition for non-supercharged cars. Class is determined by total car weight divided by total cubic inches engine displacement with a minimum of 2,700 pounds.
P, preceded by car number.
Class P – 7.00 or more lbs. per cubic inch.
Cars competing in Pro Stock Eliminator must observe the same requirements as Modified Production cars with the following exceptions.
Permitted. Maximum of 100 lbs.
Must be 1968 or later model/year American factory-produced passenger car. The use of fiberglass or other lightweight components is restricted to hood, front fenders, splash pans, and rear deck lid, however, they must be exact duplicates of stock components replaced. Lift-off hoods and deck lid permitted. Any under hood modification, other than firewall alteration necessary for engine installation, will be allowed. Roll bars mandatory; roll cages optional. Sports Cars, Sedan Deliveries and Trucks not permitted in this class. Acid dipped bodies or body parts are not permitted. Original steel body shell must be retained.
Four-wheel brakes mandatory
Engine must be of 1965 or later manufacture and must be same make as car. Any internal modifications permitted. Carburetion is limited to two 4-bbl. Or four 2-bbl. American automotive carburetors with any internal modification.
Open exhaust with headers permitted. Tailpipes and or mufflers optional. Outlets for open exhausts cannot exceed 4 inches in diameter.
Permitted however hood scoops other than ones produced as factory equipment for the specific model and year of car may not extend more than 7 inches above the height of the original hood’s surface, as measured from the base of the hood scoop.
Any rear end acceptable.
Any street equipment which does not affect the external appearance of the car may be removed, except head and tail lights and fan.
Stock front suspension for the car body used must be retained.
Slicks permitted. Rear tire tread may not exceed two inches outside the rear fenders and rear fenders must retain the original contours.
Any stock-type transmission acceptable. Transmission must remain in conventional location, determined by engine used.
Full interior trim must be retained equivalent to factory specifications. Bucket seats may replace stock seats (two required) only if they are fully upholstered and full size American automotive seats. Dashboard exterior appearance must be retained.
Weighing required of all cars to determine classification. Maximum allowable weight on rear wheels is 55 percent of total car weight.
All cars must retain stock wheelbase, length and tread width for car body used. Minimum wheelbase length 97 inches.
Full safety glass required. No plexiglass or other lightweight components. All windshields and windows must be clear, except for factory tinted safety glass. Product identification decals not permitted on any front door window or windshield. Windows must be closed; windows need not be operative.
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