'98 k1500 4.3l Vortec | Terrible Sounds!

[strikk]

Hey guys, I'm looking for a little direction before I dive into this and start making more work for myself.

1998, k1500, 4.3l Vortec, ~160k Miles, completely stock.

My trucks been sitting for a roughly 4 weeks so I decided to fire her up today, of course the thing sounds like garbage.
I've attached a very quick and raw video of the noise which seems to be coming from the oil pan area.

I've checked all of the accessories, power steering, alternator, pulleys, the belt its self and am convinced it is coming from the internals.
Fluids for the transmission, steering, oil, radiator are all topped off.

The noise increases in frequency when you give it a little gas (directly related)

This trusty guy has been zero trouble the last 3 years until I let it sit, its all my fault!

Onto the videos
Startup and engine bay: https://www.dropbox.com/s/nytsznuz9wp5i2g/2013-09-15 14.08.54.mov
Sound from underneath the truck: https://www.dropbox.com/s/1hihgt9kl4qbn1s/2013-09-15 14.09.09.mov

Any help is appreciated, thanks!

 

[GrumpyOldTruck]

I wonder if you got something in your gas somehow (maybe water? idk), mine sounded somewhat similar when I seafoamed the vacuum line.

 

[454/4X4]

If the intake was seeping, or a head gasket seeping, one cylinder could have gotten some water in it, and when you cranked it over, it kinked a rod, and now the rod is hitting the crank at bottom dead center...seen it more than once on a few chevy engines.

 

[96-1500]

Boy, I dunno but that sure sounds to me like a bad bottom end knock (rod or main bearing, caused by who knows what, possibly what suggested above).

It's hard to say not being there, sometimes other sounds can mimic an engine knock, but my 5.7 sounded the exact same way (I believe a rod bearing took a crap in mine)

If that's the case, my suggestion is swap the engine. Junkyard Vortecs are abundant and for the most part are pretty robust so I wouldn't be too scared of a used engine.

 

[USAF Long]

sounds like mine when it ran out of oil on the highway. Bad PCV I got from Zona Del Auto wasn't letting pressure out and it started evacuating oil out of my dipstick tube. I didn't know until it was too late and my oil pressure gauge started dancing and the engine was knocking. I drove it back home 45 miles at 35-40 mph like that and then on my way to the shop a few days later it chucked a rod through the oil pan.

Basically, your engine is ed. I swapped a junk yard engine in mine. Paid $350 for it I think, and I did the swap myself. Of course with the new starter, water pump, valve cover gaskets, plugs, wires, cap, rotor, coil, battery, etc... it ended up being closer to a grand.

Mine even sat for close to 8 months while I was deployed in Afghanistan and my dad fired it up maybe once a month or so and its held up good.