Anybody know what this noise is? (Vid)

[WarrenH]

....And how to fix it. 2004 Tahoe 5.3 Flex Fuel. It's louder in idle, runs good. Oil pressure is good. 207000 Miles. Thanks in advance!

https://vid.me/Wmphx

 

[baddfed]

Blown head gasket? Spark plug blown out/missing? Whatever it is doesn't sound good. Good luck with it, hopefully something minor -- but---

 

[install]

Was the A/C on? My compressor went bad causing the A/C belt tensioner to slap a hard line right below it. It kinda sounded the same.

 

[WarrenH]

Nope

 

[MO Viet Vet]

I think it sounds like a tensioner slapping around as well. Does the engine have a miss? Take the belt off and see if noise goes away.