Are you adjusting the valve lash while the engine is off? You will get a much better results if you set the valve lash while the engine is running. That can get kind of messy with oil so I take an old valve cover cut the top out enough to be able to adjust the lash.
Start on one end and back it out one valve at a time till it starts chattering. Then turn in till just after the chattering stops then turn in 1/4 turn at a time, and wait ten seconds between each 1/4 turn until you reach the full 1 turn. This allows the lifters to adjust. Run through the valves like this two times and your valve lash should be good to go.
