B3,
I totally agree that many brands of rockers leave much to be desired.....
In post #8, I was referring to this statement in Part 2 of your tech:
'It is now[ the geometric point of rotation ] at the centre of the roller axle & maintains that point throughout the whole lift range, which means the ratio stays constant as well'.
This is simply incorrect. The ratio on the valve side is from the centre of the fulcrum to the point of contact of the roller on the valve tip. This does not stay constant, it changes through the lift cycle.
Smokey Yunick says it well:
'As the point of contact of contact moves outboard, the effective ratio length of the valve end of the is increased. .......as the valve is being returned to the seat ,the point of contact is moving inboard & the effective length of the lever arm is decreasing.'
D. Vizard did extensive testing on various rocker arms, results published in his BB Chev book. He tested initial ratio, TDC ratio & overall ratio. Large variations with some.
