i believe it's to do something to the valve guide to make it the right clearance n not go straight to the valve seat right? or is valve seat next?
Once the valve guide is installed, it has to be reamed to fit the valve stem. After it has been reamed to fit the valve stem, the new valve needs to be seated in. (The valve seat should have already been done by this point) This can be done with a machine tool, or it can be ground in by hand with valve grinding compound. Once this is accomplished, the valve is removed, everything is cleaned thoroughly, and the valve is reinstalled with the spring and keeper. Normally you would do all the operations to all the valves at the same time. (That is, you don't grind in one valve, then go back and ream another valve stem. You do all the operations required at one time. So you would install all the valve guides, then ream them all, then grind or face the valve seats, then check the valve contact area, then remove all the valves, clean the head and valves up, and then reasemble into a completed head unit.)
