All of this pertaining to valvetrain dynamics and or harmonics is very true. Again I totally agree with the larger dia. push rod for rigidly and strength when you enter that category. Over the last 35 years with the development of the Sprintron, racers along with valvetrain manufactures have learned a tremendous amount. There are many ways we have found how to control and stabilize the valvetrain at very high RPM, like aftermarket blocks with raised cam tunnels along with 60mm journal bores, push rod styles and materials, shaft style rocker arms, and most important the valve spring itself. Any performance engine builder knows that push rods will flex when over coming spring pressure and big cylinder pressures. This is why aftermarket head manufactures have very generous openings for the push rods. I also agree with the sprung (return weight) returning the lifter to the base circle has a more dramatic affect, like you stated the valve and retainer. This is a major factor of cost for a racing valvetrain, buying titanium valves and retainers. But the un- sprung weight will also play a part too, I had the luxury of looking, holding, feeling push rods from a now day pro stock engine, and even though that rod was 9/16 in dia. it weighed hardly nothing as I held it in my hard, I was truly amazed. But, for the most part valvetrain stability begins with the proper spring, but when that spring pressure reaches a certain level due to RPM expected and cam profile we have to start looking at the other components for other possible weak links, like the link between crank and cam, push rods and stud mounted rocker arms. This is all really great info. for everyone to read, but back to the original question spawning this thread, for this particular engine build and application a 7/16 dia. push rod is not needed by a long shot, but the final choice is entirely up to the owner and again if Comp Cams felt like 7/16 were needed, they for surely would have that part number in the colum for this cam and lifter kit.
