If you are using stock rockers they have a wide enough contact surface to cover the valve stem so you don't need to align the center of the rocker with the center of the stem. But if you have used rockers then you should check the stem contact surface of the rocker to be sure it does not have a dimple worn into it. This will make adjusting the valves extremely difficult and if you are changing the location of the rockers and valves on the engine or taking the rockers from a different engine, cause the dimple to not center on the stem. On two engines I have had success grinding the rocker surface to just remove the dimple. I used a 7" angle grinder and went slowly stopping when the scratches started to show in the polished surface of the dimple. Both engines ran much better because I could then adjust the valves to proper lash. These were not great motors when I did this but they both ran over two years and many thousands of miles with this fix. Of course they did have oil to the rockers shafts.
If you have roller rockers then you need to get the alignment right. You can take the washers of the ends of several sets of rockers or try your source of the rocker arms themselves to see if they can provide the washers. Probably Rocker Arm Specialists can get you some washers.
Doug T
The Highlands, Louisville, Ky.
