I know this has been posted before but I would like to make sure it is still Accurate. Specs for stock Cam Lash is .019 in the Ford Shop Manual. Equivalent to 90 degree counter clockwise rotation of the Adjuster Screws from Zero Lash ? This would apply to worn Rocker Arms where the Feeler Gauge would no longer be Accurate?. Is .019 still considered to be correct or is .020 or .021 more realistic because of changes in material used when these Engines have been rebuilt over the Years?

  

Valve lash is another tuning tool.  While 0.019” is the accepted number for a stock Y camshaft, non-stock camshafts can benefit from more or less lash depending upon the camshaft itself and the results you are trying to obtain.  The Isky E4 camshaft in my 272 does like a little more additional lash just to make normal driving better.  When set to the tight side, the engine had a slight hesitation on normal take off and increasing the lash eliminated that while also increasing the idle manifold vacuum.  There’s also less rump from the camshaft with the looser lash setting but with that comes some additional tappet noise.  Regardless of the lash setting, it’s important to be consistent in the measurement or the setting of the lash so that the end results can be more accurately evaluated.

Lorena, Texas (South of Waco)