I took my valves out, cleaned and lapped them and put them back together. I also put new valve stem seals. At least on one side of my V6 Tacoma.
I performed several water tests to check the seal of valves on seats after lapping them. Had to successfully redo two valves and am down to one last dripping water, will do that next. All the three leaking valves were on the exhaust side (not sure if that's a coincidence or correlation).
I did the test by setting the engine block mating surface up and level and then filled the recession in each combustion chamber with water. Leave it 30 min to see if any of the three puddles has lost water and look into the ports to see each valve from inside for drippage.
I saw this method in a YouTube video and was wondering how effective and authentic it is in verifying that the seal is tight.