sorry bob, I was being gentle in my previous post, based on your last post I'm prepared to say that your now fundamentally wrong, sorry :-/ .......just because the piston travels further dosent mean it will induce more friction.......the reason engine designers (cough: people like me) go the short stroke route is to achieve a VERY high rod to stroke ratio, which drastically reduces piston side loading, and therefore a drastic reduction in piston friction, but this is negated somewhat by the high revving nature of these engines (due to the short stroke) which causes a shed load of friction in itself........this is the wrong way to go for a LMP1 restrictor engine as the restrictor will not permit the massive air flow required for very high RPM, as people have found when they tried to convert 5.8L NASCAR based engines to 6.0 LMP1 restrictor motors.
the piston inertia loadings at BDC and TDC are no problem, I have designed long stroke cranks, rods and pistons before, and it will be fine as long as you do the bearing load calculations correct, and select the correct bearing materials.......its certainly not destructive
the potential torsional vibration issue is easily fixed, even for the low end engine builders, as the viscous torsional crank dampers on the market are great pieces of kit at sensible cost
the reason the Katech Corvette engine makes such good power is it was designed from the outset to rev very low for reduced friction, and for its size, the stroke is quite big at around 96 to 98mm (I have the exact figure at work), this in turn reduces the friction, as friction is directly proportional to the rotational speed of the engine, as the faster the crank rotates, the more loading it exerts on the main bearings, therefore the more friction it will create.
other great examples of low revving long stroke restrictor engines are 2 Litre F3 motors, and the Ford-Elan 7 Litre GT1 engine as used in the Saleens........that thing had a stroke over 100mm and developed over 600bhp with about 850Nm of torque......all great examples proving long stroke works very well for NA restrictor engines.
believe me, a staright inlet runner aimed at the back of the valve, with a narrow runner to valve angle, is the holy grail of any engine, no matter the operating speed
......... for a head designed in the 60's, the Gurney-Weslake heads produced 520bhp from 5 litres at about 7200rpm........even by todays standards thats still great for a tuned pushrod motor