Read My Plugs

Pulled the plugs to spin the crank and noticed the even side bank is blacker. In the past they have always been the desired tan color all around. Running a Holley 4160 and thinking I've got the even side a little rich.
Left side, even - right side odd

6
5
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1

 

Well the plugs on the right obviously look better than the ones on the left..............Can't really tell much from here as it's better to look down below the electrode tip and look at the insulator to judge heat range.

I'm curious why all the threads on the plugs are so oily dirty?

 

The difference in color could simply be the adjustment of the idle screws. Typically you'd want to run on the highway and then shut down to look at the plugs. If you spend much time at idle, the plugs will be colored by the idle mixture.