1971 NASCAR International Stock Car Racing Rule Book NASCAR Grand National Championship Division Section 20-2 -- Engine

a. See Rule 1-C.

b. Engine may be located so #1 spark plug on short side of engine block is in line with the upper ball joint except on Monte Carlo Chevrolet. However, this is the maximum allowable backward position of engine. When using the small block engine -- engine must mount in standard location.

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 as specified under inspection procedures.

f. Engine displacement may be increased by boring or stroking provided the total displacement does not exceed maximum size for specified class.

g. Cylinder blocks must be production with standard external measurements in all respects with the exception of the permissible overbore.

h. Pistons optional.

i. Cylinder head must be standard production. Internal changes permitted. A cylinder head is considered to be a "Standard Production" head if:

(1) It is the required cylinder head for a previously approved complete engine, said engine being available as an optional engine for a regular factory product offering.

(2) It does not change combustion chamber, type of valve action (Push Rod) or number of valves, used in the cylinder head assembly of the approved engine.

j. Crank Shaft -- Standard production design. Stroke may be increased or decreased. Balancing permitted.

k. Camshaft optional.

(1) Rocker arm supports must be standard production in design and size.

(2) Ball or roller bearing rocker arms not allowed unless standard on volume production engines.

(3) Solid or hydraulic valve lifters optional. Roller tappets not allowed unless standard on volume production engines.

(4) Camshaft must be driven the same as approved production engine. Gear drive not allowed unless approved standard production.