Valve train geometry

Agree but getting the pushrod length right with the narrowest pattern does most of it with a stock or Iron rocker
there is moving the shaft back and forth
So if you are not moving the fulcrum you are correcting but not getting it perfect- and not really correcting with roller tip rockers- those pictures are GOLDEN
or up and down (necessary when changing to roller tip rockers as the tip curve point is raised by the radius of the roller over stock or Iron
How centered the sweep pattern is (with the sweep as narrow as possible) is a mechanical problem not a pushrod adjustment problem
with an Iron or stock rocker you have to move the shaft back and forth- but since you are usually dealing with a longer valve and/or more lift you may have to raise it also

What determines how narrow ? Tangent of line through fulcrum and pad or center of lifter and the valve stem at half lift
Tip height at half lift does not change without a lash cap so result is you have to move the shaft no fix by just changing pushrod length
What determines ho narrow a pattern is possible?
Length of the arm for example a back set fulcrum Crower has a longer arm can have a narrower pattern than a stock length arm (Chevy)
The backset fulcrum also allows the use of a closer cup to fulcrum distance for more ratio or bigger pushrods as teh cup moves away from the fulcrum too

Crane also had funny Ideas on rocker geometry- usually Harvey was with it but not his early rocker arms- or early harland sharp
ever see the ones where the arm was on top of the shaft? really funny motion
Racer Brown was the first I know of to really understand
Mike Jones Understands
I got another one for U
if you want smooth valve action what do you do to not only modify the lobe for the change in rocker ratio as lift goes to tangent and away, but on a Early Hemi or LA to account for the lifter/ pushrod angle
(same problem with porkypine angled rockers like BBC)
One thing to check on solid cams/ adjustable rockers is IS the adjuster in line with the pushrod at half lift
cheers