Most experts agree that the narrowest sweep on the valve tip is obtained when the rocker tip is centered on the valve tip at mid-valve lift...with the c/line of the rocker at 90* to the valve stem at mid lift. The drawings below are based on that. I have purposely exaggerated the size
to make it easier to understand. The rocker tip moves through an arc, based on the radius of the centre of the rocker pivot to the rocker tip. A small rocker like the SBM, swings through a tighter arc & gives a wider sweep pattern on the valve tip [ for the same valve lift ] that a longer rocker would give.
You will see from the NONSENSE of n/bomb Turk in post #54 that he thinks somehow a 1" valve lift can have a narrow sweep pattern. 100% wrong. And he thinks geometry can 'fix' it!! Nope, not when you are ALREADY using the mid-lift method above, which provides the narrowest sweep pattern.
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