I have only adjusted valve settings on truck engines - all 216/235/261 truck engines had mechanical (solid) lifters. Years ago, I adjusted valves with the engine running (after warming up the engine). About 10 years ago, I started using
this technique on a warmed-up non-running engine. This is a lot easier, less messy, and seems to give excellent results.
As stated above, if the engine has been rebuilt, or the rocker arms removed, and/or the rocker-to-valve-stem surface has been ground/polished, you can set the cold clearance about .005" wider to start and warm up the engine. Then, the valve lash can be set on a non-running engine.
