The 307 has hyd. lifters. That theary about the valves is not good. Engines can tighten up when hot when they get older. Carbon in the combustion chamber & behind the rings can raise comp. & tighten up as the pistons expand. If the battery is good you probably need to pull the starter & go through it. The ignition coil would not likely effect this. Yes. An overcharging condition will shorten bat. life.
