Yes, basically it is stroke length that makes the difference. Torque might as well be called "leverage" and a crank with more stroke produces more leverage. Of course, cams and valve timing etc would be tailored to that particular rpm, but that makes only a comparatively minor difference.Does anyone have a Torque or HP curve for this engine?
Also, what attributes are required in an engine that makes it's peak HP at direct drive RPMs vs. an engine that makes it's HP at much higher RPMs, like most Automotive engines? Is it just a matter of stroke length and bore size? Or is there more to it than that?
If you took at 0-360 Lycoming and a 350 Chevy V8, and played with cams a little they would show a very similar power curve up to 2700 rpm, both being fairly 'square' bore and stroke ratio engines.
If you look engines from WW1 to the 1920s you see engines swinging enormous propellers at extremely low rpm - all these engines had extremely long strokes compared to their bores. Far more efficient for aero engines. Even back then they felt if an engine had to go much over 1800rpm, they really ought to gear down the propeller. The engineers back then would probably cringe at at our 2700 toothpick-props whizzing around.