from the Howard Catalog

valve float over the nose
I know the Jones Motorhome cam gets up to around 300 cam lift and then dwells there- he could have made it a higher lift cam
the 440 heads stock do not flow any more over 450 or so so no use stressing springs
I've posted elswhere where the Jones has 50% more duration at .275 than the longer DC 260 cam- figure where the piston is where this dwell is around the ICL

I've posted before where setting the rocker shaft low causes the perpendicular to the valve stem to be low and that is where the maximum ratio is and the maximum leverage/ acceleration- just where the grinder is trying to slow down the valve so he can start closing it.
With proper geometry you can use less spring or make the spring the camgrinder recommended work
Harvey Crane is simplistic when he says to open immediately and close immediately
he's trying to make a point
The other important design factor IMHO is the close so there is no valve bounce
but there is more to it than just putting in a bigger spring
Actually the intake charge has mass and velocity which you want to make last as long as possible after bottom dead center where the piston is stopped.
If you hold the valve open too far as the piston is coming up you loose your velocity, you want the close ramp to work for you
and a long rod engine ha the piston come up faster, in earlier degrees, than a short rod engine
back to your comment
you do not need the bigger spring till you start to slow the valve down before you go over the nose and when you go over the nose you have to have enough pressure all the way down