This may sound stupid but I've never noticed this sound before. Got out of the car today and could hear the coolant sound like it was slowly boiling (like a slow bubbling). Anyways, the temp gauge was normal before shutting it off. I didn't notice anything until I stopped the engine at which time I popped the hood to listen and it sounded like it was coming from the passenger side of the block. I've never heard the coolant make noise like that and it really grabbed my attention. Do I just need to bleed some air out?

 

Sounds like your radiator cap is causing the bubbling your hearing. Not holding enough pressure.
Start there, should fix it.

Good luck

 

Might sound like a heater core.

 

So I could hear a slight hiss (very slight) from the cap so does this mean it was letting in air and so the system needs to be bled or do I just need a new radiator cap? The bubbling sound was definitely coming from the block/head area and not the radiator.

 

Just bleed the system when you get a new cap. LS1s are much easier to get the air out then the reverse flow LT1s, even with their built-in bleeder valves.

If you need help just IM me, I live in SD too.

Ivan