Hall-Scott hemi-head gas engines were commonly used in fire truck pumpers because of their exceptional power output. But back when this fire truck was built, Hall-Scott was only building airplane engines and a few ultra-high output car/racing engines, which is where their pedigree originated. Truck, bus and marine engines came along in the 1920s, and their OHC hemi-head truck engines didn’t need to be this big to make big power. So who built this monster of an engine in this Robinson?
According to one commenter in the know at Shorpy, it’s “a Buffalo Marine (Buffalo Gasoline Engine Co.) 6 1/4″ x 6 3/4″ bore and stroke six cylinder (1242.5 cubic inch displacement) (20.36 Liters) developing 110 hp at 1000 rpm”. And I’m in no position to second guess him. That’s what it took to make over a hundred horsepower back then, from a slow-turning side valve (flathead). Its idle speed was probably 200 or so rpm, if not less.