I had removed my passenger side header in order to replace my motor mounts this evening and saw something interesting. The number 2 exhaust port is wet and greezy, compared to the other 3 exhaust ports on that side of the block which are dark, but dry. Spark plug was little oily as well.

Is this what a bad valve seal looks like?

For reference, about 70 miles ago I had replaced the valve springs and seals with LS6 valve seals and springs. The plugs were all clean at that time. So is it possible I did something wrong?


Cylinder 2, greasy, wet, shiny.

Cylinder 4 for reference. Carboned, but dry

Dark spot on plug, oil on threads.

 

Inspect the intake valve and compare like you did the exhaust
perform a compression test and if you can without too much trouble a leakdown would be nice

I would say because you recently did the work that yes there is a high likely hood that whenever any vehicle parts are changed especially an array of them 8x 16x 32x of something, that there is always a risk that 1 out of X will have some issue. It is one of the reasons changing lifters is such a hit or miss for example, so many variables and tiny risks add up.

Oil can come from the valve guide of course. It could also arrive from the piston rings and come in with the intake charge due to oil in the intake manifold. You'll def want to find out why and where and fix it and get that plug back to normal looking before its over with. The leakdown test in particular you could apply pressure to the cylinder and fill oil around the valve perhaps you'll see some bubbles on top around the valve seal area but I don't know if you can get a good luck there or not its just an idea. You would maybe hear something though. Keep the cover off apply cylinder psi and listen carefully maybe it will help.

Since its not too difficult if your investigation is inconclusive would go ahead and just change the offending valve seals and go again, new plug of course, keep checking that plug for oil to go away when you fixed it

 

Welp, totally my fault on this one. Cylinder 2 was the last set of springs I replaced during a late night wrenching session and I forgot to put the valve seals in.

Pulled the valve cover and took a peak to confirm.

Sorry to waste everyone's time.