JCW:
As you might infer from houndog's post, the pics on the thread I linked show a plug that has had the threads removed.
The ground electrode, being attached to those threads is also gone.
What you see is the bottom of the insulator that is normally (on a not cut plug) fairly well obscured by the parts removed in the pics.
As HD mentions, there
are tools that are available that provide light and magnification for the purpose of peering down into the recesses of the plug...but it's hard to see what's going on even under the best of circumstances with the thread ring attached.
Hence, it is removed.
re: If it's too rich it is wet and black, if it's too lean, the gapped tip is often partially melted off and the ceramic is white.
If you are running too rich, your plug
will likely be wet and black, but that's not
how you tell what your air/fuel mixture is.
If the gapped tip is melted off, you have more problems that too lean. You may well
BE too lean, but again..that's not how you tell what it is you want to know......what your air fuel mixture is.
You're looking for a darkened ring at the
base of the insulator that is optimally about 1mm wide. The longer the engine is operated under WOT conditions, the darker the ring will be. Any color at the tip is not indicative of air fuel mixture. Plug temperature and fuel deposits contribute largely to that 'color'.
Don Ward, Motorsports Engineer for Autolite:
“When you tune the engine correctly, on the base of the tip of the porcelain it will look like you've taken a pencil and drawn a real light ring around the tip. That's what you're looking for when the engine is tuned correctly. If you've got too much fuel it will be a real wide ring, and if there's not enough fuel there won't be any ring in there at all -- the insulator will be completely clean."
Note he interchanges 'base of the tip' and '..ring around the tip.'
In both cases he is indeed referring to the
base of the tip.....having nothing to do with where the 'bendy thing' is (ground electrode welded to the thread ring).
How's that?
Crystal clear I'm sure.
Oh no! Belray plugs!!??? :(