ORIGINAL: speedster 1919
Charley Como made a 40 ,St made a 40. Como made a 45, ST made a 45. Como made a 51 , ST made a 51. Como made a 61, St made a 61. Como made a 90, St made a 90. This doesn't look like a bore and stroke difference to me. Prove it!!!!!!!
I have a ST S-40 and an old World Engines Catalog. The S-40 ring & ABC is listed as, bore: .846", stroke: .701", Displacement: .39 cu. in. The S-.45 was really a .46.
The point of this is that they called it a .40 when it really wasn't. They rounded the # off. The lesson to be learned is that calling an engine a .51 doesn't make it identical to another .51. As I recall, the Comos had a little lower bore:stroke ratio. Lots of parts were interchangeable but the engines were not identical.
CR