For these older engines, the copper plugs give a cooler but beafier spark.

When I say beafier I mean, the copper tip transfers the stored energy from the coil with a wider spark. The copper tip also takes a little longer in time to transfer all the energy from electrode to anode.

This allows more leeway in your tuning to burn all the fuel in the cylinder.

The platinum plugs work great on true fuel injection systems, where the atomized fuel spray is shot directly into the cylinder. This places better fumes inside the cylinder chamber.

It is the fumes that ignite not the raw gas.

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1983 500SL Euro