Ex.
xe268 comp cam for sbc has .477 / .480 lift and i thought that lift rate was pretty much limited on a hyraulic flat tappet cam by the amount of duration

xe268 for BBC has over a half inch gross lift on both Intake and exhaust

A circle is a circle to me

Why can this cam have a higher lift with out problems?

could some one shed some light?

The BASE CIRCLE is larger on the big block, thus you can get more lift and use hydraulic lifters. The real limiting issue is the lift rate and the spring pressures. Small blocks use much smaller valve springs. Big blocks use a taller and larger od. thus you can compress the larger spring more without undue problems.