Stop in for a cup of coffee

71GSSDemon said

Learning more about reading spark plugs today. Color, burn line on the ground strap, and the fuel (AFR) burn line on the porcelain. Can learn a bunch about how the engine is running. So, I cut some plugs here at work to see what I can learn. These are a bit rich, ground strap doesn't have a nice burn line visible (line should be burnt all the way to the weld point just above the threads and the fuel line on the radious of the porcelain is a bit dark, should be a bit lighter, but overall in good shape.

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There are varying opinions on the validity of the ideal strap mark and ring locations.
They do seem to corellate to the development of the flame as Shrinker described. (I'm not sure if I have that saved and that forum is gone).
However with a mix of driving conditions it becomes difficult if not impossible to say when it was rich, or lean, too much or too little timing.
The way it is, or was, done at the track is to cut the engine clean - if I get the is right, put it N or hit the clutch, then shut the engine off, keep enough speed to coast down the return road to a place to pull off. I never tried it.
Maybe more practical is to coast clean with the engine idling rather than engine braking. Then the plugs will mostly show evidence of the wide open throttle run plus the idling. Launch is pretty quick depending on your technique.

Shrinker's Spark Plug reading pdf has been posted on FABO and elsewhere. His observations make the brain explode, or shrink. Worth looking at just to see what is taken as gospel is not always universally true.

Anyway. I think those plugs look pretty good and doing what your doing helps build a baseline. If you weren't doing this you would have nothing to reference when you make future changes.