Do I need a new cap?

[heffergm]

I posted a while back about an occasional backpuffing issue (very rare) and was wondering if there was enough clearance between my pipe exit and the cap. Well, here's a pic. It looks like the installers put a blockoff plate on that the liner runs to the top of, but it extends a good 6 inches above clay exit. Seems to me it's awfully close to the top of the cap... thoughts? New cap needed? I was thinking perhaps a flue stretcher (http://www.woodlanddirect.com/Chimney/Single-Flue-Chimney-Caps/Stainless-Steel-1-Flue-Stretcher)... the other cap you can just make out is the exit for the oil furnace, so distancing the two might make some sense.

Also, I took a look down the liner. I've only had about 4 fires. The liner is black, which I'd assume is normal, but was wondering what a clean burning setup should look like (before cleaning that is). There isn't any buildup, just a fine coating. I'd expressed some concern before as well that the liner is single wall, a roughly 18 foot run (I'm guessing, I need to measure). It runs through a masonry chimney that's partially inside the home for about 3/4 of its run.

 

[Captain Hornet]

Your cap looks almost exactly like mine. You have wire mesh on yours which I don't have but the spacing is far apart so it shouldn't hurt you. The cap attaches to the masonary in the exact same way. Your flue liner sticks up as much as mine. I first thought that it was too close to the cap and would hinder the draft but I found that it works fine . Your top plate holds the liner up high and that helps to keep water out of the flue. Your fine setup looks exactly like mine and I don't know why you would want to change a thing.

 

[heffergm]

Your cap looks almost exactly like mine. You have wire mesh on yours which I don't have but the spacing is far apart so it shouldn't hurt you. The cap attaches to the masonary in the exact same way. Your flue liner sticks up as much as mine. I first thought that it was too close to the cap and would hinder the draft but I found that it works fine . Your top plate holds the liner up high and that helps to keep water out of the flue. Your fine setup looks exactly like mine and I don't know why you would want to change a thing.

Accepting what you say, my only other concern would be the fact that my boiler and stove exits are on the same level, which I understand is a bad thing, as the smoke exiting one can downdraft down the other.