Oh god... get out of the 60's!! Yeah, maybe back when... when there were no screw-in studs, chrome moly push rods, roller rockers, Stelite alloy or Stainless steel valves and the average cam (Duntov style) had a very wide .030" lash (hence the old term "30-30 cam") which literally beat the crap out of the valve tip. Keep this in mind. Almost EVERY Honda, Toyota, VW, Mitsubishi, Nissan, Volvo and so on have over head cams, right? Those cams use clearances between the followers and the valve, which makes it a SOLID follower. Do THEY ever need adjusting? No. If a valve is going out of adjustment, it is because something is moving, wearing or bending. Press-in studs used to pull out. Stamped steel rockers used to beat the crap out of the valve tip, not only mushrooming the valve tip itself, but flattening-out the rocker tip as well. Pushrods used to bend and all sorts of other problems, but these days everything is so strong and stable, nothing wears, bends or pulls to make the valve adjustment go oyt like it used to. We run solid roller cams in some of our street and street/strip engines with an average of around .600" - .680" lifts with no need to re-adjust anything except maybe once every couple of years... if that.