1968 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Circuit Section 20-21 -- Cooling System

a. Water pump impellers may be altered.

b. Removal of fan, fan belt or air cleaner not permitted. Any NASCAR approved air cleaners allowed, and they must have the complete element. This applies to all late model divisions as well as speed trial and record attempts.

c. Interchangeable radiator cores are allowed providing they do not alter sheet metal or frame of radiator for make and model. Radiator must remain stock appearing.

d. Radiator dust screens permitted.

e. Any brand or make of radiator hose or hose clamp permitted.

f. Radiator overflow pipe may be relocated or extended to not more than six feet.