[1968GTO421]

Originally Posted by HWYSTR455

Well, OE service intervals are usually 24k miles for standard points ignitions, but Ford duraspark ignitions I think list 12-15k miles. Think about the same is listed for HEIs. These are of course 'standard' plugs, with standard electrodes.

Beyond a certain year, the electrodes changed to a different material, so you have to take that into account. For example, there are a number of Cadillacs that go 100k before a 'tune up'.

Just because a plug 'looks' good doesn't mean it's performing 'optimally'. They can 'work' beyond the recommended interval, but I'm pretty sure the performance will be down.

MSDs and other multi-strike boxes, ones that increase rise time on the coil so they saturate more, wear parts faster, not just plugs either. Like caps, rotors, wires, and coils, all wear faster when under a heavier load. There again, just because they 'look' good, doesn't mean they are performing optimally.

Plug wires are one of the items that most ignore for the longest time, thinking they 'look' good. Blows me away when folks say they haven't changed them in 5+ years and countless miles. I've seen cheap sets last only for hours, really. The best ones I've seen last like 2 years or so, max. If you handle them a lot, less.

Follow general service intervals, or at least use them as a guideline for what intervals work for you. Depending on the system, it should be in the 12-24k miles or 2-3 year range.

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Thanks for info I had forgotten but used to know....have been getting info overload on these forums