Honda cbr250 revs to 19k with steel valves and valve springs! I had one that had done 60,000kms and it still wouldnt blow when taken to redline, the valveguides suffered and so to the head gasket, its all been done before by people much cluey-er than me, my tip, buy a blown cbr250 motor for $100. measure and weight the internal bits and from there you can build a *****in half scale F1 v10, 72' like a renault easy, or hard 90' like ferrari.
Thats my dream, anyhows.