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A 600 cc motorcycle engine with 4 cylinders has only 150 ccs per cylinder. A typical 350 CID V8 has 712 ccs per cylinder. Thus the motorcycle engine only has to move the piston up and down CUBE_ROOT( 712/150 ) = 60% as far per stroke (if it had the same bore stroke ratio. But since it does not those little pistons only move up and down 35mm per stroke (versus 89 mm for the big V8) so the little pistons can move up and down 2.5 times as fast with the same relative tension loads in the connection rods. So while the big V8 tops out around 6K RPMs the little motorcycle can top out at 6K*2.5 = 15K.
Now with the pistons operating in the right area (speed and strength wise) all it takes is a vlave train and intake and exhaust systems to also operatin in these stratospheric areas. 4 Tiny valves can move up and down much faster than 2 great big valves. Making them out of Titanium saves 50% of the density, so the only thing to manage is the springs needed for these valves to follow the cam.
The small European V8s that rev to 8.5K have shorter strokes so the piston speed is (basically) equivalvent to the big V8s and the motorcycles. The Ferrari engine that I am familiar with, use Titanium con rods to save weight, the crankshaft is turned on a lathe from forged billet, and (or 5) tiny valves. The intake and exhaust systems on these cars have more room in the engine bay to enable the intake systems and exhaust systems to be designed for performance rather than occupied-volume.
Together, the short strokes, exotic parts selectioni, and perfectly tuned intake and exhaust systems is what enables these engines to spin at these rapid rates, and produce large amounts of power per unit displacement.
You might be surprised, that the actual power-output per unit engine-bay-volume is actually better with the Vette LS2 engine than with the Ferrari 360 engine. Since the big V8 with push rods operating at a leisurely 1.5K RPMs driving down the road at 65 MPH is still in the fat part of the TQ curve, the big V8 can get better gas milage than the smaller higher strung V8 of the Ferrari (even after one puts in the overly-tall 6th gear like the Vette has). Pushrods enable an engine with big power to occupy a small volume and still deliver great power to the user (in both TQ and HP terms), and simultaneously deliver great gas milage.