Has anyone ever seen this before? Is it serious?

 

I noticed that the Adel clamps I used to secure spark plug lines put a discoloration on the spark plug lines where the clamps were mounted above the cylinders, that is, where they get hot after shutdown.  I suspect the rubber in Adel clamps has some kind of outgassing characteristic that stains nearby elastomers which soak up something oozing out of the rubber clamp lining.   Just a guess.  Interestingly, where the spark plug wire passed  inside the clamp – no discoloration.  Next to the clamp, where the wire enters and leaves, the red spark plug wire is stained black for about ½ inch, tapering off with distance. 

 

It had me scratching my head for a while until I realized that the particular clamps in question got the post-flight heat soak from the fins on the cylinder head below.  It does not seem to bother the spark plug wiring.  As for Tygon, I cannot  say.

 

Fred Moreno