Engine Knock- Need Help!!!

I have a 1999 Jeep Cherokee Classic that has 162xxx miles. Started getting a bad engine knock that is present from start up and when fully warmed up. I took off the valve cover and noticed some sludge.

looking at the engine running with the valve cover off the 1st two cylinder pushrods are not letting as much oil up to the rockers as the others. I changed the oil with a high detergent oil and some risolin to help clean it out.

I am thinking maybe a couple of the lifters are gummed up from sludge. I have looked and listened to other videos posted that sound similar to mine but never mention a resolution so any help is appreciated

http://www.youtube.com/watch?v=H3CxkvrPYYw

Thanks!

1999
4.0L
Automatic
np231

Wow, I thought mine had a loud knock.

Others will have to chime in here...but it sounds too high pitched to be a rod...probably lifters.

I would seriously look at replacing or overhauling the engine. Sludged engines are on their last legs- no amount of engine flushes or treatments will ever make it right again.

It sounds like a piston in the video.