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Discussion Starter #1
I spent the past couple of days sorting through a number of items on my Giulia SS - car is relatively new to me and I have been slowly going through the various systems - car was running and driving well yesterday morning other than a rattle which I believe was due to a missing nut on a bolt on one of the exhaust flanges. Work done since yesterday:

Adjusted idle mixture on all cylinders using Colortune
Replaced exhaust flange bolts (6)
Checked fuel levels in carbs - rear was low so adjusted float and replaced needle and seat
Addressed small oil drip at oil filter (canister style) - adjusted gasket and tightened filter housing
Moved tach cable out of the way of oil filter housing and clipped to frame rail using existing clip
Synchronized carbs using synchrometer and set idle speed to 700 rpm

During the carb synchronizing process car was idling for a long while and did not notice anything amiss - after I wrapped up and took the car for a short drive I heard an odd vibration / buzzing sounds as RPMs built - took it back to my garage and thought it might be some sort of fan interference. Car ran fine during drive - no issues w responsiveness or power.

Fan looked clear - am a bit stumped what could be causing this and am concerned it could be a bigger issue - links to videos of car idling and at the buzzing sounds at higher RPMs are below - any thoughts would be greatly appreciated.

Thanks.

Idle 1 - YouTube
Buzz as RPMs Build - YouTube
 

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Hi

Your engine is moving a little too much at 700 rpm. A more precise carburation + ignition adjustment. But nothing really important.

concerning the noise, it's very strange. first time I hear this. it looks like a problem with a spark plug ... (but really not sure !)
remove the spark plugs and inspect them.
try changing all 4 spark plugs, to see if the problem persists. check HD leads connection.
 

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Discussion Starter #3
I forgot to mention in the list above that I had also replaced the air plenum gasket - the new gasket I used is apparently a bit less thick than the old one which is now causing the bottom of the plenum to just barely touch the top of the intake manifold and at higher revs = loud metal on metal vibrations.....
 

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Then, remove the plenum and start the engine to see if the noise is still there :)
 
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Discussion Starter #5
Problem diagnosed - plenum and thinner gasket (approx 1.5mm) was the issue - now I just need to find a source for the thicker Venice plenum gasket to raise the bottom of the plenum slightly above the top of the manifold. If anyone has a source for the thicker (3-4mm) believe plenum gasket please let me know. Thx.
 
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