Yesterday I was mocking up the T&D sport comp rockers on my sons engine. To do this it necessitates removing the 2 rockers from the shaft, mounting the shaft to the head, and using the supplied tool to determine the correct height on the head to calculate the correct push rod length.
What did I find in the rockers? The exact same system I designed over 30 years ago including bearings and oiling. Sometimes being lucky is better than engineering. What this taught me is using needle bearings IS a good thing and I'm glad I did it. This engine sees a lot higher RPM than my GMC. J.D.
PS. A slide rule is a ruler with something in the way when your trying to draw a straight line.