the valves are hydraulic.
First things first.. if you are using a fram oil filter, STOP.
Purolator or Wix.
the fram's cardboard backikng plate slips and causes the filter to be obstructed. when the oil gets hot and thin enough it finally reaches the top end, but sometimes.. not as much as it should.
What I would also do is change your oil, run 10w30, NEVER 20w50. and substitute 1 quart of Marvel Mystery Oil for 1 quart of oil. This will gently and thoroughly clean the engine, as well as clean up any crud that's making your valves tick.
