OK, then if that is true, why is it any different to have 2 seperate orfices, one at the bottom of the oil feed line and a second larger one (in diameter) at the top of the oil feed line, then if it were simply one longer orfice in one position in the oil line? In other words, my orfices are approximately 1/16" in size (not diameter but length of the orfice hole in the brass set screws.) If that orfice length was instead 1/4 inch in length all in one position, say at the bottom, why would having 2 seperate 1/16" long orfices create further restriction then one longer orfice? When I was running solder in the bottom fitting with a hole drilled in it, as was the standard for many years on knucks running newer oil pumps, the length of that hole varied from around 1/4" to 3/8" depending on how much solder I got filling the fitting. That did seem to restrict total flow muchmore then the small brass set screw orfice.
I'm not trying to argue. I'm accepting what you say as factual, but asking for more information for my own knowledge. I am concerned that I may have too liteel oil flow to the top end now, but there isn't a good way to test for that short of pulling the heads apart to inspect the shafts.
There really isn't. Without making your eyes glaze over by throwing hydraulic equations at you I'll try to explain. There are varying equations that describe how different types of restriction behave; the orifice or rapid contration is governed by a specific equation, as the length of the restriction increases, this portion is governed by another set of equations which are more readily applied to pipes (or tubes). So one could actually calculate the length of this elongated restriction by seting the two equations equal to each other and solving for the equivalent length of restricted tubing that would equal the same headloss created by the orifice. Therefore, we could create the same flow reduction as two orifices by splicing in a single length of smaller diamter tubing into the top end oiler tubing. In your example the difference in headloss created by the varying length of the orifice is insignificant, especially when compared to the headloss created by the restriction itself.
In regard to adjusting flow by rotating the rocker arm shafts, I believe this feature was for '39 and earlier models only, and I think you would need the early rocker arms. On page 30 of the original '40-47 shop manual it says that "Oil to rocker arms and valve stems is metered through a fixed orifice in each rocker arm shaft and no adjustment for more or less oil is provided".