To help in getting an accurate adjustment, I trim the feeler gauge tip to about 1/4 inch wide using a sharp sheet metal shears.Even with refaced or new rockers, it doesn't take long for the valve stem to wear a slight depression in the rocker end that contacts the valve.Hopefully your valves are not recessed into the head , this throws off the rocker geometry, resulting in more noise and wear.Even if the seats are replaced ,its no guarantee the valve stem heights are close to correct unless you check them yourself.
I have lots of free time,lol, so I can check the valve lash on one cylinder at various degrees of cam rotation before the cam opening flank closes up the lash and starts opening the valve.As I stated earlier, the tradition valve adjustment techique varied the lash by at least .005 depending on where you checked it. On my engine setting the valves one at a time etc,keep the lash as constant as possible.The engine is happy, more power and less noise.Does all this fussy crap matter on your vintage engine?Maybe not ,but you'll never know unless you try.Oh yeah , if you take too much time messing with the valves, the engine will cool down some and maybe affect valve clearances as you go through the procedure.
46forme, I have never used a vacuum guage on an after market cam.It may be better to do the valves on a modified engine with feelers as the highest vacuum at idle may not mean much when the engine is reved beyond the original stock limits. Try it and post the results.
