Hello Everyone, i just got my 308gts back from service and they said they adjusted the valves. The engine makes a verry metallic noise, i think it comes from the valves. Let me know what u r thinking? here is a link to a video: [ame=http://www.youtube.com/watch?v=UhmYgU0xQxQ]MVI1299 - YouTube[/ame] Thank you! Cheers axel
Good day Axel, To me the noise sounds like a vibrating washer... which would imply an untightened nut somewhere, which is not good. Needless to say, it should be checked. That being said, it is very helpful that you can re-create the sound for your mechanic. Cheers, Sam
Thank you Sam, i called my mechanic who was supposed to adjust the valves and take care about the engine. He said that the valves are allways a little bit loud on the 308. Is this true? Cheers axel
To me it sounds more like the ignition is set to early and makes the engine knock. The noise is only there when you accelerate?
It does sound like a bit of spark knock. I've always wondered if it would be audible all the other noises the car makes!
Good day Axel, To me that sound was not valve noise. Valve noise frequency would tend to follow the RPM's, whereas I did not find this correlation. If the valve clearance was a little "loose" then the noise would attenuate or disappear as the engine heated up. Again, the sound does not sound right...Maybe's its the recording and/or YouTube? Regardless, I would expect your mechanic to check it over just to be sure... the issue could be nothing or could be something that could cause future engine issues. I am curious if you can recreate the sound when the car is stationary and by revving the engine? If so, then your mechanic can simply use a stethoscope of even a rubber hose and listen to areas of your engine for the noise location. Cheers, Sam
+1 I'm going to try to record that sound on my 308 & make it a ring tone. Axel, I hope that ignition issue gets addressed soon by your mechanic. Your car sounds great otherwise.
My 300zx turbo gets that sound when I boost the turbo beyond the octane of the fuel. Sounds like pinging to me. Like someone cracking a deck of metal playing cards. I'm no expert so don't jump all over if I'm wrong. Just putting that out there.
John, it sounds too heavy for detonation and too regular. I think it is mechanical. What exactly was done to the valves??
Sounds lean on 1 carb , the ignition ping may be from the lean cylinders. A IR thermometer will show the leaner headers as having different temps from the others.
Thank you. In answer to this, I can honestly say I have absolutely no idea because my engine does the exact same thing, but only above around 3700rpm. My engine is newly built as I just built it, and it's perfection yet I have no idea what that rattling sound it. I've run it on a dyno and tuned this engine to the sharp end of perfection and it runs perfect and is tuned perfect, but it has that rattle and I have no idea what could be causing it. It's something mechanical, I just have no idea what.
I have come across a metallic rattle before when someone forgot to tighten one bolt on one of the timing covers.
If your mechanic has retraced all his steps of every nut and bolt loosend, removed and replaced and all parts are proven tight, and it's not an ignition/timing issue.. I would remove the belt on the air pump and take it for a test run. It may be ready to explode.
That definitely sounds like pre-ignition to me. I'd try retarding the timing a few degrees which should stop it. If you continue to run it in that state it won't take long to burn a hole in the top of a piston.
Another place to check, and assuming the engine is ok, you might check for a loose bolt or rivet on the engine cover slats.
I have the exact same sound and have evaluated and experimented with timing to no end and it's not timing. At least in my case it's not.
Just listened again on good headphones - does it ever do it under light load? It definitely could be early detonation as others have pointed out. Usually described as "BB's in a can being rattled". Sounds like it stops as soon as you let off the throttle to switch gears...chances of a rattle disappearing like that seem slim. In addition to a timing issue, could also be low quality fuel.
