Quote Originally Posted by sleeper1500 View Post
Cam's .580 lift on Comp XE-R lobes, which are fairly aggressive. Not worried about them breaking, my concern is them losing there pressure. 348# of open pressure is rediculous for a hydraulic roller under .600, but then again this is my first LS.
Your frame of reference is off a little. The open spring pressure is not primarily determined by lift. It's determined by the weight of the lifter and max RPM potential of the cam being used. The higher open spring pressure is needed to control the vertical opening inertia of the heavier hydraulic roller lifter. This higher pressure is why the cams in these engines are billet, and not cast. A cast cam would flex too much at higher RPMs due to the high spring pressures and break.

The seat pressure is also higher to control the heavier lifters on the aggressive opening and closing ramps that roller cams allow.