1971 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Division Section 20-4 -- Carburetor

a. Carburetor must be NASCAR approved. Approval of carburetor shall mean approval for all competitors and cost of carburetor shall be a factor of consideration for approval. No external alterations permitted.

(1) Rocker arm hemispherical combustion chamber engines restricted to one four-barrel carburetor having 1 11/16" throttle bore.

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

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

(4) Engines with staggered valve design restricted to one four-barrel carburetor having 1 11/16 inch throttle bore.

(5) Intake manifold unrestricted within manufacturers line, readily available to participants. Materials optional.

b. Fuel injection or superchargers not permitted.

c. Jets may be any size.

d. Carburetor restrictor plate must be used when furnished by NASCAR. The 4150 and 4500 series carburetors may be used on any approved engine. Only approved carburetors with a 1 11/16" throttle bore opening are permitted.

(1) The 4150 carburetor is permitted to use a 3/8" spacer, with 1 11/16" holes, furnished by NASCAR, to provide carburetor butterfly clearance between the carburetor base and the NASCAR restrictor plate [sic - .]

(2) The 4500 carburetor is permitted to use only gaskets at the carburetor base.

(3) Only a maximum of three 1/8" thickness gaskets are permitted under any carburetor.

(4) Gaskets cannot be altered in any manner.

Only approved carburetors with a 1 11/16" throttle base opening are permitted and the approved carburetor cannot be altered in any manner.

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.