Speedmaster spark plug holes improvement??

TurboGLH said

I prefer champions, but I'm running 5224s because I could get them at the parts store. I feel like the extra electrode length helps unshroud the plug.

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I believe the RC12YC should be available and any parts store. At least I've not had a issue. It's basically a magnum plug (just smaller hex socket than the original RN12YC)