When discussing camshaft design, no one as yet has made comment on rocker flex, and how it will affect the valve lift curve. The Vincent rocker is extremely weak from the stiffness viewpoint, and the amount of flex that occurs in a running engine is considerable. If this is not allowed for in the static design, the end result will always be considerably reduced dynamic valve lift curve
Has anyone tested a rocker to see how much it flexes ? For those interested the attached illustration shows the method. If the X1 dimension is 300 mm, and the X2 dimension is 50 mm, an 8 to 10 Kg weight is sufficient, but the measured flex will be an alarming amount.
For a really stiff rocker, the flex should ideally be 0.002" but up to 0.007" is passable, and above 0.007" the valve lift loss will start to become excessive.
The flex is due to the lack of depth in the arms, and the inadequate material around the pivot.
This situation is impossible to realistically improve on while still retaining the stock installation arrangement, but the modified rocker mounting illustrated in an earlier post presented an ideal opportunity to improve the rocker stiffness dramatically. Unfortunately in the photo it seems not to have been done.