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L28 engine making pinging/ticking sound

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Hey everyone, I had a thread a while ago about the same issue on my 1976 280z with a relatively recently rebuilt L28 with round top SU carbs but it's still reoccurring and I wanted to start a new one because it's been a while. I have adjusted the valve lash, replaced the spark plugs, and gotten the carbs slightly better tuned. After replacing the spark plugs the first time the sound went away, but I think this may have been a coincidence and it just randomly happened to not be making the noise at that time or it was quieter because the choke was on and I didn't hear it. Adjusting the valve lash did not seem to make a difference and most of the valves were perfectly in spec and a few were just barely off. I didn't see anything obviously wrong under the valve cover. I think the carbs are tuned in roughly the right area just from checking spark plugs, but they are definitely not like 100% dialed in. The car was running very rich prior to this. The noise seems to quiet down when the engine is warm and when the choke is on. I'll attach some videos of the car cold with the choke off (IMG_7122), warm with it off (IMG_7123), and warm with it on (IMG_7124). As you can hear, the noise is definitely loudest in 7122. I have used a stethoscope and I can't really seem to find the noise. My best guess is somewhere along the exhaust manifold or headers, but the exhaust always makes noise obviously and I can't tell if it's just normal noise I'm hearing or the pinging. The sound is not coming from the block, valve cover, or head as far as I can tell. It definitely seems to be coming from the drivers side of the engine. I'm thinking it may be a leak from the exhaust manifold or headers, but the engine was rebuilt a few hundred miles ago so the gasket must be new. I might just tighten up the nuts a bit and see if that does anything. If not, maybe try replacing the gasket. It's driving me crazy trying to find out what it is, anyone got any ideas? If you have any other questions/info just ask me and I will provide it. I can take more videos tomorrow but I won't be able to this weekend as I am going camping and won't have my car. Thank you for the help.




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It's obviously really hard to diagnose a random noise from a video; but you may be on to something regarding the headers.  An exhaust leak from the headers can sound a LOT like valvetrain noise.  When you try retightening the header bolts, go from inside bolts to outside bolts, and do it in steps so you're gradually clamping the header to the head evenly across the surface.  If that doesn't work; remove and inspect the header gasket.  If it's leaking, you may see some telltale signs of the leak(s) on the gasket material itself.  Don't assume that the engine builder used the correct gasket for those headers...I've seen plenty of people install the wrong gasket for their particular head & header combination.  If the gasket is correct, and a quality gasket, you can try using some copper hi-temp RTV on the sealing surfaces to help battle any leaks.


Hope this helps -- good luck with it.

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