[Barry_R]

It sounds like you are pulling the heads anyways. Pull and swap out/rework the lifters. At this point it needs to be done - 2-3 hard seasons is enough especially with marginal spring pressures.

When you remove them look carefully at the backside of each lobe - beyind max lift. I'm beting you se an indentation where the lifter "landed" after each opening event. If you remove the springs you'll also see signs of metal transfer around each keeper/retainer interface. All signs of valve float and loss of control. You may not hear it - but with those pressures it is happening.