That would be zero valve lash. You only use a feeler gauge on solid lifters.
It has nothing to do with the lifters getting use to your driving style. Lifters rarely loosen up. Lifters wear over time, thus causing the gap to widen, creating lifter clatter. On solid lifters, that is why they must be adjusted periodically. On hydraulic lifters, this is not necessary, as they automatically adjust for the gap due to wear, if they were installed and adjusted correctly in the first place.
For a 1969 Lincoln, the point gap is set at .017, and the spark gap should be set at .035.
set gap at .028
I set the gap to .028
the gap should be set at .044
set you gap at .031
what to set gap on j8c spark plug
There is no valve adj on a 4.0l it has hydraulic valve lifters.
this car has self set hydrolic lifters.
You have to put proper gap for lifters and use marks to make sure that timing and the positions of camshafts are correct.
THE GAP SHOULD BE SET AT .054".