I'm guessing your timing chain jumped, either because the chain has stretched or the guides or tensioner failed. At 160k, the chain definitely should have been replaced by now. That would account for the noise, oil loss, and everything else. If you haven't lost coolant, then head gasket, etc. are likely fine.
-I took it to a local shade tree mechanic (who didn't necessarily seem shade tree until i saw his shop) who also said it sounds like timing chain, but he tried to back that claim up by sending me a screen shot of some stored engine codes for P0011 and P0366, cam shaft sensor exhaust and intake
-After leaving there, I made an appointment at my regular mechanic for tomorrow, mentioned possible timing chain issue, and the tech that answered the phone said (basically) these cars NEVER have timing chain issues. Which now makes me doubt the competency of a place that has a 100% success rate in diagnosing and solving every problem with this car. He, however, is not the tech that always works on my car.
I'm actually surprised you said this. I'll explain why.
I was getting the car towed by a guy i have used and recommended many times. Good, honest guy I trust. Not that it matters, though. As we were pushing the car out of the parking spot and into place for loading, another guy stops by and jumps out to help. Turns out he's also good friends with the tow driver. Long story short, he tells me he's a mechanic and just "finally got rid of a solstice" that a previous customer refused to pick up. Mentions that he still has most of the engine left from it, and asks me to start the car so he could hear it.
I start it up again. Nothing at idle. Slight rattle at throttle, he said probably lifters. I spend about 50 minutes talking to the guy really trying to feel him out. I was about to spend a good chunk of money to have it towed over 60 miles to a good (but not cheap), honest, reliable shop i've used for every repair on this car without issue. But his shop was only five miles away. I recently had the cooling fans replaced because they completely crapped out. Module went bad. So I told him a little lie and asked if he could fix that first. Just to see what he would say. He ended up calling someone from the nearby GM dealership and asking them, who basically told him step by step what my usual mechanic told me he did to diagnose the problem, so I wasn't too impressed but at least he had his channels. I took a gamble and agreed to have it towed to his shop.
I get to his shop and immediately decide no ****ing way. Not a single driveble car there, they were all junkers. But I decided to play a little more. I started the car after it was unloaded and drove it about 15 feet into his shop bay. Interestingly, there seemed to be absolutely nothing wrong with the car. It sounded normal. It was always a little rough while it was warming up, but after a few seconds it was smooth. Nothing but the tick of the fuel pump. It drove nice and smooth into his bay.
Once inside he starts telling me that's weird, and that he'll "warm it up and take a look and call me tomorrow" so I said "well why not do it right now." So we do.
Starts up fine. Idles fine, but after a minute or two there is a very very faint rattle from the bottom side of the engine on the passenger side. When first pressing the throttle hard, you can hear what kinda sounds like turbo bearings, but nothing like the noise I heard when the trouble started. The noise eventually quiets down under sustained RPM. All in all, the car seems like it's mostly fine again. Mind you there still hasn't been a single CEL through any of this, only an oil light twice (once when the problem first occured, and once again when I started it eight hours later. I don't mean that I was starting it and driving it around with the oil light on AGAIN today!). The mechanic also agrees that there doesn't seem to be anything MAJOR wrong with the engine, but asks me to take him for a test drive before I decide what to do.
We get in the car, back out, and I begin to leave the lot. As soon as I start giving more than a little throttle, there's a rattling from the engine and the wurrr sound comes back. Mechanic tells me to stop the car, it gets quiet. Tells me to go again, and again the noise comes back once I really try and "go." Leaving the car in drive, he gets out and opens the hood to listen. When I push the gas while it's in drive, it rattles pretty good from the passenger side. Again, still NOTHING like it did in the first place, but definitely not anything I've heard before. He concludes it's timing chain. We go back in the shop and he proceeds to wheel out the exact same LNF engine from the car in the story he told me in the parking lot. Spins it around, shows me where the timing chain is and explains what he wants to do to the car to verify it. What worries me is he said the reason they pulled that engine in the first place is "because of the timing chain, but we couldn't figure out what else was wrong with it" immediately I think
b) you broke everything trying to change the chain without the proper tools
c) the repairs you TRIED to do caused enough damage that you had to remove the engine, and at that point you were basically holding the car ransom by demanding a ton of money to return a car that is in seriously worse condition
d) i love my baby way too much to let you ever touch her
I told him to hold off on doing any work on it. I was at this point 100% convinced he was trying to take me for a ride. I know who I bought this car from. I know how long he had it. I know exactly what he did to it and when. The timing chain was replaced at 125k miles, when the water pump was replaced for the second time. No way the chain is bad already, unless there's more to the story inside.
So I call my regular mechanic to set up an appointment for tomorrow, and mention that i think it's timing chain related, and, surprisingly, the tech who answered said it's unlikely.
He said "do you know how many times i've seen a timing chain issue on one of these cars?"
i said "probably all the time"
he said "no, only once."
I didn't ask him how many of these cars he's seen, but the way he immediately dismissed the chain all together makes me suspicious. However, there is one specific tech that they ALWAYS assign to my car every time I take it, and this tech on the phone was NOT him. The one who always does the diagnosing on my car is 100% spot on each time.
I'm going to take it there tomorrow either way because they're a good shop. Even if it comes down to rebuilding the top half of the engine, I know they will do the job right, to spec, and provide an excellent warranty.
sorry for the long story, but i'm just really passionate about this car and anything to do with it