I've been running through several iterations trying to obtain the ideal valvetrain geometry but am finding that there are physical limitations.
Using photographs I've taken of the rocker arm as it cycles through, I can adjust the pushrod length to bring the rocker height perfectly in line with the valve tip. That is, at mid lift, the rocker arm is exactly halfway through it's motion. For all intents and purposes this is the ideal with loss of information from the cam and minimal sweep across the valve tip. Of course I'm after the narrowest possible contact patch however at what point does a compromise have to be made and forsake perfect geometry for reasonable contact positionally speaking?
We all know the factors that affect pushrod length. Block decking, milled heads, gasket thickness, valve stem length (over stock), lifter seat height, rocker arm style, etc but some items end up fixed such as the distance from the rocker stud to valve centre line.
I've attached a few pictures of the valve tip witness marks.
I'm looking for opinions.
I'll also post up (later) the pics form the rocker arm cycle with the mid-lift method data points overlayed.
For the record the specs for the engine in question (although I'm involved with several at the moment):
Gen 1 SBC, RHS Pro Torker iron heads w/.100" taller valves, Comp full roller rocker (1.6), Comp 15853 (short travel) hydraulic roller lifter w/2.66" seat height, .570" lift.
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