1961 NASCAR International Rule Book Specifications NASCAR Grand National Championship Circuit Section 21-8 -- Engine

a. NUMERALS INDICATING THE HORSEPOWER RATING OF THE FACTORY MANUFACTURED ENGINE ASSEMBLY MUST BE PAINTED ON BOTH SIDES OF THE HOOD IN NUMERALS AT LEAST EIGHT INCHES HIGH.

b. The engine size displacement recognized by NASCAR as stock for a particular make and model is listed in Grand National Specifications chart.

c. No polishing, porting, altering and/or relieving of motor parts except as specified by NASCAR.

d. Any evidence of grinding or enlarging intake or exhaust ports or passages in exhaust or intake manifold, cylinder head or motor block will be cause for disqualification.

e. Oversized oil pans and oil coolers are not to be used unless approved by NASCAR.