[82 GT]

It all depends on how long the intake and exhaust valves hang open. I've seen cams with lifts as high as .565-.580 with no piston to valve clearance issues simply because the duration was not very long. I admit, most of these cams I speak about were custom cams. It's all in the lobe design on how quick the valves open and closes(duration as most of us call it).

Think of it this way: Suppose you were trying to wack my hand with a hammer before I pulled it back. It's not how far I reach my hand out...it's how long I leave it out there before you get a chance to wack it. Now suppose that the timing of me putting my hand out and you swinging the hammer(and missing) is the same sequence over and over again just like the valve timing of an engine....you always come close but always juuuuust miss me.
Now say I decide to leave my hand out there(same distance) for a split second longer(more duration) and your swinging timing is the same......BAM.....Smashed fingers!!