I ran a round track 350 for several seasons with a roller cam and triple springs. It's just necessary to reduce the diameter of the valve guides enough to get more springs in there. They wear out camshafts in a great big hurry, but they allow very high RPM before the valves start floating.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!