1973 NASCAR International Stock Car Racing Rule Book NASCAR Grand National ® Championship Division Section 20-1 -- Competing Models

INCLUDING
WINSTON CUP GRAND NATIONAL, GRAND NATIONAL EAST
and GRAND NATIONAL WEST DIVISIONS

America's greatest auto race drivers competing with the finest equipment developed by America's automotive manufacturers.

The specifications for the Grand National Division, in essentially the same form as listed here, have been accepted by the Automobile Competition Club of the United States -- FIA and by the FIA for inclusion in the Apendix J. They will be listed in Category 5B of the special touring sedan section.

a. NASCAR Winston Cup Grand National races are open to steel bodied 1971, 1972, 1973 models of American-made passenger car production sedans.

NASCAR Grand National West races are open to eligible 1970, 1971, 1972, 1973 models of American-made passenger car production sedans.

NASCAR Grand National East races are open to eligible 1970, 1971, 1972, 1973 models of American-made passenger car production sedans (Including eligible 1970, 1971, 1972, 1973 Grand American Challenge Series cars as classified under Section 20A).

Category 1--Standard size cars.

Limited to cars with a minimum of 119-inch wheelbase, a maximum engine size of 430 cubic inches piston displacement, standard body size and complying with minimum weight requirement as set forth in paragraph 1b. (OVERBORING: A total maximum of one cubic inch will be permitted for overboring because of cylinder wear).

The following 1973 cars have been classified in Category 1 --

The following 1972 cars have been classified in Category 1 --

The following 1971 cars have been classified in Category 1 --

The following 1970 cars have been classified in Category 1 --

Category 2--Intermediate size cars.

Limited to cars with a minimum of 115-inch wheelbase, and less than 119-inch wheelbase, a maximum engine size of 430 cubic inches piston displacement, standard body size and complying with minimum weight requirement as set forth in paragraph 1b. (OVERBORING: A total maximum of one cubic inch will be permitted for overboring because of cylinder wear).

The following 1973 cars have been classified in Category 2 --

The following 1972 cars have been classified in Category 2 --

The following 1971 cars have been classified in Category 2 --

The following 1970 cars have been classified in Category 2 --

Category 3--Compact or GA Cars. (Not eligible in this division)

Limited to cars with a wheelbase of less than 115 inches, with a maximum engine size of 335 cubic inches piston displacement.

Category 4--Sports cars. (Not eligible in this division)

Category 5--Grand American cars. (Not eligible in this division)

b. FIA category 1 and category 2 Standard approved bodies may run with 305 or 430 cubic inch displacement engine equipped with one four-barrel 1 11/16" carburetor.

(1) All FIA category 1 and category 2 cars, regardless of engine displacement, must weigh a minimum of 3,800 pounds ready to race (gasoline, oil, water, etc.) without driver.

(2) Cars with approved size engines (305 to 430 cu. in.) may be required to use a carburetor restrictor when furnished by NASCAR. ACCUS has approved a differentiation in the carburetor plate opening size for hemispherical versus wedge type engines, as defined by NASCAR.

(3) Any weight added to car must be located within body shell. Special cars including the Mercury Cyclone Spoiler, Ford Talladega, Dodge Daytona, Dodge Charger 500, and Plymouth Superbird shall be limited to a maximum engine size of 305 cubic inches and a minimum weight of 3,800 pounds equipped with one four-barrel 1 11/16 inch carburetor.

c. Eligibility.

(1) It is mandatory that a street version engine be produced by the manufacturer as a regular production option for installation and sale to the public in a regular product offering. The 1973 eligible bodies will be volume production models as selected and approved by the ACCUS. Engine production requirements will continue to be 500 engines installed in cars before approval to compete is granted, and in the case of engines reduced to 366 cu. in., 500 identical basic engines must be produced and installed in cars before approval to compete is granted.

(2) Production models and production engines introduced by January 15, 1973, will be classified eligible for competition in 1973. New models or engines introduced after January 15, 1973, will not be eligible for competition until April 15, 1973, if approved by ACCUS. Any equipment introduced after April 15 will not be eligible during 1973.

The following characteristics must be identical with the production engine upon which recognition of type has been granted:

CYLINDER BLOCK
Material
Number of Cylinders
Angle of Cylinders
Number of Main Bearings and Type
Integral or seperate Cylinder Sleeves
Location of Camshaft
Overall Configuration

CYLINDER HEAD
Material
Number of Valves per Cylinder
Type of Combustion Chamber
Location of Spark Plug
Orientation of Spark Plug
Arrangement of Valves
Type of Valve Actuation
Number of Intake Ports
Number of Exhaust Ports
Center Distances of Intake Ports
Center Distances of Exhaust Ports
Shape of In & Ex Ports at mating faces of manifolds
Angle of Port Face relative to mating face of Head to Block
Firing Order

GENERAL
All parts must originate from stock production castings and forgings which have been machined according to the normal machining schedule utilized for standard production parts. They may be subsequently refined, modified and improved by further machining or rework.

(3) The ACCUS car classification committee will determine if the eligibility requirements have been met.

(4) All eligible engines can be used in the standard size (Category 1) or the intermediate size (Category 2) cars.

(5) There will be no weight or displacement handicap on any car or engine in 1973.

(6) Maximum engine displacement for Category 1 and Category 2 cars is 430 cubic inches with a total maximum of one cubic inch permitted for overboring becasue of cylinder wear.

(7) All model, engine or equipment changes or modifications not governed by NASCAR rules Section 20 c (1), (2) and (3) must be submitted for consideration of approval, not less than 30 days prior to the date of intended usage in NASCAR competition. The applicant will be notified of approval or rejection no less than 15 days before the date of intended use. Any equipment which does not conform to specifications or tolerances contained in the NASCAR Rule Book, will not be eligible for approval during 1973.

NO CHANGES FROM THE ACCUS APPROVED STANDARD PRODUCTION AUTOMOBILES OR COMPONENT PARTS WILL BE PERMITTED EXCEPT AS SPECIFIED IN THE FOLLOWING NASCAR RULES FOR CAR PREPARATION: