Any reason for this?

[Limited Ex]

Working on replacing my rocker arms, I have the infamous ticking under the hood, and after I got the upper intake off, I noticed the channels in the rear were much more dirty than the ones in the front. You can see the difference, its a steady increase from the back to front. Is there any reason for this? Something I should be concerned about?

 

[mrboyle]

Its not that uncommon. Its due to the air entering the intake carrying the oil from the crank case vent.

 

[Limited Ex]

I just remember the first time I took everything apart down to the lower intake, and they were all equally dirty. But that was also the first time ever I had taken it apart. I just wanted to make sure that I did not under-tighten something or put something back where it didn't belong