DUF, stay with the whizzer 7/8th valves. Your motor will have plenty of power.
If you decide to go bigger you'll need to go all the way....Bigger valves, bigger piston, webber cam,and some trick stuff.
Here's my H motor,
Heads been shaved all the way down, super small combustion chamber. Fred's big valves, webber cam, Mikuni vm18 carb cut down and lightning piston...knife conrod and crank.
Head, valves, piston,and jug have all been coated with a thermal barrier,(heat coating)
Ray
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