The method you use may be at issue although I'm a bit skeptical it's the cause of your miss. See post 14 of this thread for a concise explanation of the best way.
Valve Lash Setting
If the exhaust is opening- adjust inlet valve lash; inlet closing - adjust exhaust valve lash. This requires you to do each cylinder individually but it goes surprisingly fast.
Is your engine cutting out (elect) or is it stumbling (fuel)? Could be a bad plug wire (or more) or arcing between wires. What type of distributor are you using?