Probably a SB 25.63 Speed Twentyfive motor. Possibly 1937 or 1938 as fitted with a magneto. Typical Works photo taken on a dirty floor and not much attempt at fine paint finish and greasy marks on the rocker cover! Reply
Alvis Archive 
Probably a SB 25.63 Speed Twentyfive motor. Possibly 1937 or 1938 as fitted with a magneto. Typical Works photo taken on a dirty floor and not much attempt at fine paint finish and greasy marks on the rocker cover!