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They run hotter and retain more heat in the head. This will tend to cause detonation and or run-on. (diesling) Generally, every heat number you can go down (colder) you lose from 70-120 degrees of tip (cylinder / chamber) tempature. Platinum plugs are on the same level, but closer to the 100-120 degree mark.
I found running Autolite 42 platinum plugs made my 427 run 25 degrees hotter than a standard copper plug. Because the MSD fires a full spark 20 degrees of crank rotation the platnium plug is not only not needed, it will contribute to overheating, the afore mentioned detonation and everything else heat causes.
You may not be experiencing any of these symptoms. If not great. Spend the money on more expensive plugs. MSD's position is it won't be of much benefit if any at all.
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michael
A man that is young in years, may be old in hours, if he have lost no time. But that happeneth rarely. Generally, youth is like the first cogitations, not so wise as the second. For there is a youth in thoughts, as well as in ages... Sir Francis Bacon (1561-1626)
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