For many years I always made my own plug wires using copper wire with soldered on ends. I never had a problem. But today, I've finally given in, and am using factory made modern wire sets. Much easier to find and save lots of time. I cannot tell a difference in starting. If I were looking for a weak spark problem, I"d start on the low voltage side, i.e. every connection from the battery clear up to the points. A dirty, oily, or poor connection at the ignition switch, ballast resistor, coil, or distributor can cause weak spark. Poor starting can have many other causes too though. For me personally, intake leaks have been the most hard to find and to isolate, although more on small engines than on stovebolts. Some modern coils don't need a ballast resistor to be used with them. If you have one of those, and are also using an external ballast, that could cause low spark voltage.
