Thanks for the interesting explanation regarding the "oil" that occurs at the base of some plugs.  Souinds logical to me, like, fuel reverting back to it's original constituents? (never could spell)     Your plug is what I refer to as the straw brown coloration.  If the other 7 appear like the pictured example, then I'd say you nailed it.  Several years ago I purchased from Harbor Freight, an inexpensive inspection camera under $100 with it's own monitor. Works pretty good - comes with a clip-on mirror that attaches to the camera tip for added viewing angles, like, valves.   I believe inspectrion probes that attach to a cell phone can be of better quality.  

64F100 57FAIRLANE500

The consensus I've seen, is it isn't actually motor oil. A slight bit of fuel vapor over time, theory goes, seeps into threads and polymerizes or whatever into a kind of oil. I know exactly what you're referring to, saw it just this morning when a plug is removed notably even on a flathead, it can have that characteristic film. I just wipe it off the plugs no breakdowns yet!

I was thinking of getting an inspection camera for smartphone, something like that, just to take a peek inside the cylinder, can they be rotated to see the valve color too?

And now to completely hi Jacque me own thread, you know how when you look at a set of well loved cylinder heads, the valves will have different colors. Sometimes you'll see only a couple that are running a sort of whitish color. This is commonly attributed to those particular cylinders running lean.

But I've also read, what's really going on is the whitish colored valves are the correct mixture, it's the dark valves that are running too rich. I've seen some A&P websites that discuss what a happy exhaust valve looks like, the aviation folks take a lot of interest in that, and it's kind of interesting. I run a pretty sharp tune so I want to keep an eye on it. The plugs look real good as far as I can tell.

You would haveto have a look at all 8 and compare one against the other.  I can only say from my experience that if all is as it should be, that is, no vacuum leaks, properly tumed carb, properly matched PCV valve and plumbed correctly etc, then all plugs will be fairly uniform in color.  In my case, all are a similar straw brown in color.  I'm sure there is a lean and a rich cylinder but all 8 seem to run pretty close. At least by comparing plugs. I'm sure others will chime in that have flowed these intake and heads who will be able to answer which cylinder(s) they are.       Please forgivve me for not starting a new thread but why is it that a couple sparkplugs will have an oily base just below the hex when there are no visible oil leaks??

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Hey gang I was talking to someone who was carburetor tuning their 6 cylinder and with those long intake runners discussing how it can sometimes be difficult to achieve uniform fuel mixtures, one particular cylinder will typically always be leanest.

I got to wondering is there an equivalent thing going on with the Y-Block due to its intake design? I ordinarily check #5 spark plug for a quick check as access is easiest but too lean is something to look carefully for, along with preignition, or spark knock. Seems like the way the center runners are stacked it might be different, but I dunno? Is there a particular cylinder to watch?