The distributor cap (also referred to as a dizzy cap) is one of the three main components which serve to get each spark plug to literally 'spark' and ignite the fuel-air mixture. The other two components are the rotor arm and HT leads -- both of which are difficult to upgrade and simply need to be replaced when worn. The dizzy cap however can be uprated to a certain degree.
Copper is an excellent conductor and by adding copper contacts to a dizzy cap its transfer of electricity is improved. Another advantage is that the standard contacts degrade very quickly and after 6 months can have an excessive amount of oxidisation build-up. With copper, this doesn't happen.
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