You need to go back to the basics to check out what you have and its total relationship with the other components of your engine---heads milled to increase compression-----effects valve to piston relationship (clearance)
Cam---cam timing to crank effects valve to piston relationship(clearance)
Heads---clearance between valve retainer, seal, guide effects how much cam lift can be used
Valve springs--spring pressure effects tappet following cam lobe and rpm---