Topic: Weird sound as revs drop
As of yesterday we managed to get an engine to actually fire up while mounted inside our car. I'm shocked at how well it runs honestly, but there is one thing that has me a little worried. If I rev it up to about 4,000 rpm and then let off the gas completely and suddenly, the engine makes an odd grinding sound as it spins back down to idle. It's not terribly loud, so part of me think's I'm just looking for problems that aren't there, but I've never heard this from any other car that was running well.
Does anyone know what would be causing this? Is it something I need to be worried about, or is this just to be expected from a 23 year old engine?
For context, the engine is a N/A straight 6 out of an 87 Supra.