Chevrolet founder Billy Durant, who previously had owned Buick which had pioneered the overhead valve engine, used the same basic engine design for Chevrolet: exposed pushrods and rocker arms which actuated valves in the detachable crossflow cylinder head.

This was referred to this as a "valve-in-head" design, and it drew considerable publicity in a time when most rivals were flatheads.

For its last year (1928) it gained a revised carburetor, higher compression, aluminum pistons, and larger valves for a rating of 35 horsepower (26 kW) at 2,200 rpm.

Because of increased weight of the slightly longer 1928 Chevrolet National Series AB performance failed to improve from the 1927 Chevrolet Series AA Capitol.

It had the same bore as the 171, but a longer stroke of 5+1⁄4 in (133 mm), giving it 37 horsepower (28 kW) at 2,000 rpm.