In what context do you mean you built a cam... Are you talking about welding and/or grinding an existing one?
You can increase the lift easily with an existing cam by grinding the heel. At total valve closure and for part of the rotation, there is no contact between the lifter and the cam lobe heel... If you grind off at this point it will increase the lift by the amount you grind off. No need to harden if you're careful. If you want to play with duration, etc, you will need to weld/grind, weld/grind, Harden. Or not Harden, if you don't mind a short lived cam.
They used to do this on old Harley's decades ago for drag racing.