Hello everyone, recently i have been restoring this camaro I bought of a seller. After doing a ton of work on the car I went out to take it on a test drive. That’s when I first heard this sound. (I will attach a video below). After trying to diagnose it I have had it happen while the car was in park and I was revving the engine. It seems to only happen under heavy throttle application when the engine is above about 3500 rpm. I have narrowed it down to either the fan hitting the shroud or detonation knock. If anyone has a good ear for this stuff i would really appreciate some input. I haven’t found any witness marks of the fan chewing up the shroud but that was just a quick glance over while having a smoke. going to go out tonight and inspect the blades and the shroud with a flash light to see if there are any scratches.

Video link of sound: