Through your process of elimination it might be time to pull the oil pan. The noise consentration apears to be in that area. Might be a good time for a bottom end inspection. Check all the bearings and inspect the camshaft. There is some excessive clearence somewhere. And like you said the noise is loudiest from the bottom. There is a simple trick you can do. It involves turning the engine over by hand with a socket wrench on the harmonic balancer. It can be done in many positions where you rotate the engine maybe 2 or 5 degrees in one direction then back in the other direction to see if you can feel any slap in the bearings, you should be able to feel it. There is going to be slack from the timing chain depending on mileage. If you play with a little bit you should be able to tell the difference. I would try this before I pulled the pan.

 

On having another thought, the type and weight of engine oil might play a part in the noise you hear. An upgraded oil they recommend is Mobil 1 0W-40ESP. The fact that the noise increases when the engine warms makes me wonder if the oil is light and is thining enought with excessive bearing clearence causing the noise. Not knowing what oil you use is only a speculation. For experimentation you could try a thicker oil and notice any changes. I'm just being courious. On the AFM systems they are going to heavier oil for that system. Others have said that a heavier oil pump by-pass spring is recommended to increase the oil pressure, but the heavier spring would do little at idle with no oil by-passing. Just a thought I had, I'ts raining today so low activity day.

 

I didn't realize that it had General Motors notorious AFM system. That noise might be something associated with the AFM trying to disassemble itself which has happened fairly frequently since it was implemented years ago. Back in about 2012, my Chevrolet service manager told me that they had to replace about 1 engine a month due to AFM failures. He said some of them were catastrophic failures.

 

C-7 and C-8 had the AFM system until 2019 then they went to the DfM system. I think GM dropped the system before last year when Trump dropped the gas mileage standards. The system was good in theory, but all the minor issues created a bad storm for a lot of engines. GM started using this systm in 07, I had a 013 Avalance 5.3 that did not have that system, great engine. But with the extended oil change intervals with light viscosity oil, low oil pressure, factory cleaning and bearing clearance issues they beat themselfs to death. They can be fixed if they haven't distroyed themselfs. If you have a 5.3 or a 6.2 and you want a easy bypass it you can buy the AFM deactivator for $150 and plug it into the OBD2 port

 

Another possibility is the DMF Duai Mass Flywheel. I'm not sure what you have, a 1 piece flywheel or 2. The 2 piece has springs in the center that can go bad, and then they rattle. When placed into gear and letting the clutch out does the noise go away?

 

A quick Google search reveals that the C7 and C8 Corvettes still use AFM. My 2023 C8 Corvette has it and I am currently using a CarByte AFM eliminator module.

 

Shark from what I hear If you upgrade your oil grade, and don't go 15K miles on a service, and use the eliminator you shouldn't have any issues. I think if I was going on a long road trip across country and wanted to conserve fuel I think the system would work good. But driving around town where the system is off and on constantly is really hard on the lifters at low rpm and low oil pressure and dirty oil. They say to listen to the lifter tick before issues start. Right now I have nothing with the AFM or DFM system. The 022 Silverado 2500HD I have has the 6.6L Gas No DFM. It runs great no oil issues, no cylinder Knock, only con is 16mpg. I will put up with that with a basic engine with no mechanical issues. I need to check out these DMF flywheels that have been using in Corvettes, I'm not familiar with them, and sometimes have issues.

 

Fonatig, It is a possibility that your clutch could be making that noise. There was a YouTube where a guy had that same noise, and they decided it was coming from the DMF assembly.

 

Not positive but everything I could find online says that the C7 and C8 Corvettes only used AFM. I agree about using the AFM delete module solely in town because it does go in and out of it very easily, even under moderate load conditions. I got about 30 mpg bringing it home from the Museum to Kansas City. You have to use the specific Mobile One oil to maintain the warranty and I let my dealer do it once a year because I don't have enough miles to warrant a change. Plus I have no way to lift it change the oil myself.
My son's Dodge Ram used a system called MDS and it cost him a new engine. And it started off with just a slight lifter tick that got progressively worse. It doesn't sound like any of the systems have been perfected yet.

 

30 mpg is very impressive, is it worth it if you might need to replace the engine in a few years, that's the question. Always wondering if you are going to have an implosion problem. Having the dealer change the oil is a good idea, its hard to dispute there records if issues come up. And which oil should you be using today. One of the issues I see with cylinder deactivation is carbon build up on intake valves and piston tops. dealerships are always pushing top end cleaners for the valves and fuel system. I still think the oil catch can on the PCV system helps. I install them on all my new vehicles The service manager at the dealership also agrees they help on direct injected engines. Shark, best of luck on your sports car. By following all the recomdations you should be good.