OldIHC

6 volt ign doesn't like resistor wires use solid core wires if useing a 6 volt coil.

Valve springs can be removed without removing the head. Use a valve spring compressor designed for a flat head engine.

I removed a spring from my engine a few months ago, no problem. Just make sure you don't drop the retainers into the sump.
The sparkplug can be removed and the valve can be knocked (lightly) using a wood dowel if the retainers are stuck.

back to original question, I owned and rebuilt quite a few 214 motors, and if I remember correctly all of them had a little putt putt at the idle, not sure if it's just the nature of the old motor, distributor slop, nature of the carb, who knows,
but I could get them idling real smooth, except for a random putt here and there, bugged me early one but I got over it, I tune them now more for "performance" timing rather than smooth idle