There are 2 types of distributor cap wires. The high voltage coil wire comes out of the top of your distributor cap, and links it to the high voltage coil. This wire can withstand voltages of up to 1300 VDC. The other wires coming from the distributor cap are the spark plug wires, and they are the wires that carry the spark to your engine's cylinders. They are far lower voltage. In either case, the wires should be well insulated on the outside, so the voltage remains on the inside, where it belongs. Be sure that the sparkplug wires are not spongy or leaky, with displays of arcing visible to the eye.