Thread: spark plugs
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Old 01-09-2012, 06:37 AM
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Tom Wells Tom Wells is offline
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Cobra Make, Engine: E-M / Power Performance / 521 stroker / Holley HP EFI
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sspano01,

I have a couple of "mild" street 385s, one 521 with Ford aluminum CJ heads and one 557 with Edelbrock heads and about 9-1/2 compression. One is EFI and one uses a Holley.

The CJ heads use SP-447 (AGSF32C) Motorcraft plugs just fine. I change them every 5K miles or so whether they need it or not

The Edelbrock heads use the Champion RC12YC plugs.

Each set is gapped at around .050" according to the MSD spec.

I've tried other "higher tech" plugs and regretted it every time. You may or may not have the same experience...

Tom
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