gmt400 1999 GMC Yukon SLT Engine Problem

[Blackandgold51]

I have a 1999 GMC Yukon SLT with a 5.7 liter V8, and the problem I have is when the engine is running there's a little "knock, knock, knock, knocn" noise like an old beat up 70's American Car. The Engine does run fine nonetheless, but that "knocking" sound is the only problem.