[Mr.Fixit]

Your shortblock's limiting RPM is the critical piston speed. The longer the stroke, the further the piston must travel per rotation, so it accelerates faster at any given RPM compared to a shorter stroked motor. The radpid changing of direction of the piston puts big loads on the conrods, which will stretch and try to oblong the big end's bore. If you get the shortblock to stay together with high qaulity parts, then the next obstacle is the valvetrain.Reduce it's mass as much as possible, so there is less inertia to resist the valve's wanting to change direction so rapidly. This is where overhead cams have an advantage, no pushrods, rockers and a tiny lifter. This is also where titanium valetrain parts become more necessary, they weigh less. But, then again, i have driven several bigblocks with over 4.3" stroke that readily see 8000 rpm in every gear, with nothing exotic at all. mechanical tappet cam, steel rods, all 60's stuff. Your odds of sawing your motor in half do go up dramatically with RPM, you are pushing your parts closer to their breaking point.