kaibiagi Posted October 8, 2023 Share Posted October 8, 2023 Engine seems to be making like a pinging sort of noise at idle. It's around 800-900 rpm in this video, and I shut it off after in case it was damaging something. The carbs are definitely way out of tune, and I think it's been running very rich. What could the sound be coming from, or is it something not to worry about? Thanks IMG_6798.MOV Quote Link to comment Share on other sites More sharing options...
jhm Posted October 9, 2023 Share Posted October 9, 2023 No, I would definitely worry about it; and not drive it anymore until you’ve diagnosed it. Did it just start making this noise out of the blue? Or maybe after you’d done some repairs or maintenance? It almost sounds like a mechanical interference noise. Use a stethoscope around various locations on the engine to help isolate where it’s coming from. Quote Link to comment Share on other sites More sharing options...
bunkhouse Posted October 9, 2023 Share Posted October 9, 2023 I'd pull the valve cover and take a good look to see if there's any loose parts. Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 9, 2023 Share Posted October 9, 2023 Didn't listen to the video and don't know anything about the history of the vehicle but the simplest thing to do, if it's an L series engine, is to pop the valve cover and look around. They are known to throw a rocker arm occasionally, especially after sitting a long time. Sometimes a valve keeper too. More details about what you're working on will help. Quote Link to comment Share on other sites More sharing options...
kaibiagi Posted October 9, 2023 Author Share Posted October 9, 2023 Only thing I've done recently that is engine related is attempt to tune the carbs. I definitely did not do a very good job and will take it to a professional to do it better, but I can't see that having caused this and it wasn't doing that when I finished. I have not touched timing or anything else. It was running very rich before I touched the carbs and it still is, I don't think my efforts changed much. Engine was rebuilt maybe 300 miles ago by a professional shop (PO had that done), and has been running totally fine until I started it up at the time I took the video. Has been sitting around mostly the last month since I have taken ownership as I have worked on other areas of the car, and unknown how long before that. Doubt it was anything super long though for such an old car. It is a 1976 280z, so L28 with round top carb conversion. The sound definitely seems to be coming from the top of the engine. I haven't looked into it with a stethoscope yet, but that much is clear to me. I can definitely pull the valve cover when I get the time and take a look. Is the gasket reusable? Let me know if there is any other info I can provide that would help. Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 9, 2023 Share Posted October 9, 2023 It could just be that a valve guide was tight. People have had them pop off for no apparent reason. Usually after revving. The gasket should be reusable. I used the same gasket for many removals in the past. A 300 mile gasket should be fine. Beside the noise, it's a good idea to check valve lash on a new engine after it gets some miles on it. Beware though, today's camshafts have been known to flatten a lobe easily, soon after installation. It just happens. Hopefully it's not that but be ready. Post some pictures. Good luck. Quote Link to comment Share on other sites More sharing options...
kaibiagi Posted October 9, 2023 Author Share Posted October 9, 2023 Sounds like a project for this weekend. I'll take a look under the cover, see if anything is obviously wrong. Haven't done any of this stuff before, so I may come back for more help but I imagine all this stuff should be in the factory service manual and on YouTube. I'll probably add some more pics of what's under the valve cover if you guys have any more insight. Thanks for the help. Quote Link to comment Share on other sites More sharing options...
kaibiagi Posted October 15, 2023 Author Share Posted October 15, 2023 update: replaced spark plugs and sound went away. Quote Link to comment Share on other sites More sharing options...
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