This topic comes up on Speedtalk, it's because hydraulic cams don't have "lash ramps". What those exactly are I don't know, but I'm guessing the initial ramp of the lobe may be milder than a hydraulic to take up the lash smoothly so it doesn't slam closed the clearance, but that's a total guess.
This is what I remember being taught in my auto shop classes many years ago. The "lash or clearance ramps" that solid cams have are not needed on the hydraulic cam from what I remember. Its is right where the valve starts to open. It lets the solid lifter take up its lash adjustment and come in full contact with the cam lobe smoothly or as smooth as it can. Hydraulics dont really need these ramps since they have no lash and are always in contact with the cam lobe. Ron
