Learned valve lash with a feeler gauge in 1998, now I just watch the scanner
Back at my uncle's shop in Gary, Indiana, you set valve lash by hand with a feeler gauge and a wrench, and you felt the drag through your fingers. Now on most of these new motors I don't touch a rocker arm, I just hook up the scan tool and watch the misfire counts on a screen. Some days I miss getting my hands in there, but I don't miss burning my forearm on the manifold. Any of you old guys still keep a set of gauges in your box or did you finally toss them?
My old boss in Indiana had the same story, said he could feel a bad valve through the wrench before any gauge told him. I read somewhere that some new motors don't even have a spec for it anymore, you just swap the whole rocker if it's off.