My 1960 engine has not been active for about 7 years. I didn't know how the plugs would look when I took them out. I was pleasantly surprised to find them all in good condition - nice colour. I have replaced them with Champion J12YC. It will be some time before I know how these plugs perform as I have decided to pull the engine and Transmisson. The plugs which were in there were of a name and number I had never heard of.
Spark plug replacement is interesting to me particularly on cars that I drive a lot. That is because as you say, the condition of the plugs when you take them out is VERY revealing. If the cars just sit around a lot and only get started occasionally without being driven this will tell you next to nothing.
Most generic shop manuals give a page or two of color pictures that show what various plug conditions indicate.
Paul
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