340 or 408?

@Newbomb Turk mentioned it in an earlier post. Longer strokes increase motoring friction. The increased stroke will breathe deeper at lower rpm and thus make more indicated power. So long as the airflow is higher by enough to keep the indicated power high enough to overcome the increased motoring torque (friction torque), the engine will make more brake power (output). At some point, the frictional increase MAY get high enough to overcome the additional airflow and the power will be either equal or less (ie. the power noses over earlier). Obviously this is describing only the same engine with a different stroke.

You can also see the opposite effect. Some will DEstroke the engine and the motoring torque (friction) will go down. Then you spin the engine fast enough to breathe more air and with the lower friction, you can make equal/more power at some higher rpm. It's all just simple physics actually. It also shows why the stroked engine generally makes peak power at a lower rpm and is normally higher, just not as much of an increase as the torque increase.