I've never heard an engine knock before so I can't tell if that's what's happening. It's a knocking rattling sound somewhere around my engine, but it's very inconsistent, and only does it when the car warms up, and at a certain RPMs. It's an 84 z28 with a 350 swapped into it. Can anyone help? I've just pick this car up. Wanna build it but if it's knocked. I'll trade it.

 

Could you take a video of it making this sound so we have something to go off of? cars can make all sorts of bad sounds, hard for someone online to say "yep your engine is knocking" without hearing it.

 

I can try tomorrow, but I'm not sure how I'd put it up here.

 

Make a you tube video and post a link to it. From your description, it sounds more like detonation or ping than a mechanical problem.