1968 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Circuit Section 20-22 -- Carburetor

a. Carburetor must be available production model in manufacturer's line. No external alterations permitted.

(1) Rocker arm hemispherical combustion chamber engines restricted to one four-barrel carburetor having 1 11/16 inch throttle bore when used with box-type manifold, or one four-barrel carburetor having 1 3/4 inch throttle bore when used with log-type manifold.

(2) Overhead cam type engines restricted to one four-barrel carburetor having 1 11/16 inch throttle bore.

(3) Wedge type engines permitted either single four-barrel, two four-barrels or three two-barrel carburetors with 1 11/16 maximum throttle bore.

(4) Engines with staggered valve design restricted to one four-barrel carburetor having 1 11/16 inch throttle bore when used with box-type manifold, or one four-barrel carburetor having 1 3/4 inch throttle bore when used with log-type manifold.

(5) Intake manifold must be of conventional design readily available to participants. Materials optional.

b. Fuel injection or superchargers not permitted.

c. Jets may be any size.

d. Wedges permitted.

e. Heat risers may be blocked.

f. Any NASCAR approved gasoline filters may be used. This applies to all late model divisions as well as speed trial and record attempts.