What kind of problem in this engine that is making this knock noise in the 1998 Yukon

[Blackandgold51]

http://www.youtube.com/watch?v=ZGNqC9Vm9MM

 

[90chevstepside]

In the last video it sounds like the lifters are chattering..

 

[Blackandgold51]

In the last video it sounds like the lifters are chattering..

Are you sure that it's not like a rod-bearing or something like that?

 

[Blackandgold51]

In the last video it sounds like the lifters are chattering..

By the way, nice truck