Valve train noise is mostly a matter of keeping the adjustment accurate, as the rate of lift changes rapidly once the clearance is taken up as the cam transitions from the clearance ramp to actually lifting the valve off its seat. Just a slight bit of extra clearance at the rocker tip produces that distinctive rattle that some people think is "normal" for a stovebolt valve system. Somewhere stashed away in one of my storage bins there's a set of "silent lash" adjuster screws. They have a spring loaded ball bearing in the screw tip that keeps a little bit of tension on the rocker arm all the time, and pretty much eliminates valve train noise. I don't think the idea worked very well, as the only manufacturer I know of that chose to use a similar setup was on a Ford 240 cubic inch six made in the mid-1960s. When Ford upsized that engine to 300, they didn't include the silent lash system.
Jerry
