TOPIC: NHT rocker shaft evolution

In the 1949 beginning there was NHT " low pressure oil system: with scrolled shafts until around 1966. Rumored that many earlier atlas shaft upgrades started earlier. 1966 may have been the date ALL NHT were made with the high pressure oiling systems. This included the wide gear oil pump version with 6 start drive gear.

shown is early low pressure rocker shafts.
3 different versions of early low pressure rocker shafts are shown. In all cases, the "flats" face the valves!

1.At that 1966 time frame, the upgraded high pressure rocker shafts were solid surface with only a single oiler hole, approx .093", facing away from the pushrods, toward the valve springs.
This version of shaft has terribly small wetted surface within the rocker. It must have been later deemed as inadequate. @.007 in/sq
2. The next version added ground-in flats on the shaft around the little oil hole, growing the wetted surface area, .193 in/sq, which is 27.5 times more wetted surface area.
This hugely improved wetted rocker area, during cam lift, oil is swept from the front toward the underside of the shaft, which is now double loaded by the compressed valve spring.
3. The pushrod rocker ball is only lightly lubed by slowly migrating oil and seems to be an adequate amount. This type is carried over from the early low pressure scrolled rocker system. I have not yet heard of problems unless the balls are improperly replaced in the rockers and the holes are misaligned during installation.