1968 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Circuit Section 20-12 -- Engine

a. See Rule 1-a.

b. Numerals indicating the cubic inch displacement of engine must be painted on both sides of hood in numerals at least eight inches high.

c. Internal polishing, porting, altering and/or relieving of motor parts permitted.

d. Maximum two valves per cylinder.

e. Oversize oil pans and oil coolers are not to be used unless approved by NASCAR. Oil pans must have a minimum ground clearance of five inches.