Universal laws of physics. Specifically, highs (high pressure) seek lows (low pressure). Remove a valve stem and the air flows out of the tire or inner tube. Why? Because the high in the tire/tube seeks the low outside the tire/tube. If there is a high over Dayton on the weather map and a low over Toledo the wind in Lima will be out of the south. Why? Because the high in Dayton is seeking the low in Toledo so the air flows north. The high under a wing (caused by deflection) will seek the low above a wing (vacuum) and the wing will move up (lift). The high will seek the low but the wing is between them. Moving the wing up, because highs seek lows, is lift. This may be an over simplification, but universal laws of physics do not change (ie: at 5252 rpm torque and HP are ALWAYS equal).

Have to agree with cjshaker on this one. He stated that his explanation was "general speak" and his general observations are spot on.

While yes it is technically possible to create a long stroke motor that can achieve and withstand high rpms (ie 7800), it also comes at a cost ($91,000 in the example given), with every component being modified (we're not talking stock FE parts here) and many parts constructed from unobtainium (hence the 91k price tag).

I once viewed some engineering videos where 3 single cylinder engines were constructed identically with the exception of bore and stroke. One had an equal bore and stroke, one had a larger bore with shorter stroke, and one had a smaller bore with longer stroke. All 3 engines were identical in displacement, identical valve sizes, identical cams, carbs, and heads.

The engine with identical bore and stroke was tested first and used as a baseline. The test measured hp, torque, and max rpm. Compared with the square engine the short stroke version topped out at a higher max rpm, the long stroke version had a lower max rpm. I don't recall what the hp differences were between the three, but the long stroke version did make the most torque.

If the long stroke engine in this engineering video had been modified (larger valves, different cam, lighter rod & piston, head work, carb work, recurved ignition, etc.) then I imagine it too could have achieved the same rpm or higher than the short stroke motor. But when all things were equal, the short stroke motor achieved the higher rpm (as cjshaker was saying).