Put another way, the Sportwin has a Bore of 2-⅜" and stroke of 1-⅞" – for a piston displacement of 16.6 cubic inches.
The Fastwin has a bore of 2-⅜" and stroke of 2-¼" for a piston displacement of 20 cubic inches. Increasing the bore to 2-½" gave them 22 cubic inches and three more horses.
Error corrected – 😳
