Stopping the knock: Lower compression and ported heads...

The issue of tightening the valve lash is an interesting one. A guy from racer Brown Cams spoke about it 2 months back, but I didn't quite get it.
The way I understand it now is that by closing up the lash clearance, it makes the lifter/pushrod/rocker arm and valve more accurately follow the lobes. The valve actually "sees" more of the lobe. The key factor here is that a tighter lash makes the intake close LATER, which should reduce cranking compression.