The suggested springs jwt states def are not suited for 8000rpms. The HD springs are def required and highly suggested over the ones jwt suggests. The springs go into harmonic flutter and will not control the valve past 5500 rpm. Anytime you go with a solid lifter/cam outfit spring pressure has to increase go control valve action and increased harmonics. I've tested both springs and jwt suggested spring is inferior. Don't always go by manufactures suggestions. Put the book down.
