Drawing says ream 3/8" and shows ram as 3/8".
1" stroke does sound too much for that engine, he did use 1" stroke for the larger horizontal pump but 1/2" stroke eg 1/4" offset is more likely. By comparrison my 2" Fowler is 3/8" bore x 3/8" stroke.
Edited By JasonB on 20/08/2019 20:41:07