Tired of DIY!

YR
gotta agree with you even if it was a different topic
on a SBM even with stock rockers the geometry gets off with High Lift cams
and when you put any roller rocker, longer chevy rockers and/ or longer valves you can get into trouble real quick as shown using your example
There is a difference between geometry- the way I see it, and having the rocker tip/ roller somewhere near the center of the valve- at least not coming off the edge which is what the backspacing solves
you can have the half lift fulcrum position correct height - which IMHO is geometry- and still have to backspace
and as you said- just raising the shafts makes it worse and a second go around with new stands or Mike at B3's spacers are required
Magnums require a different fix