Hi,
Working on the project card which was running and idling nicely on petrol.
Pulled the plugs which were very old - #4 came out , there was no ground electrode and what turns out to be a thread insert is stuck on the plug.
Compressions are very good on the other 5 cylinders, assuming the same for this one, so trying not to pull the head off.
Am trying to find another insert to use, all of the common ones so fare are 15.7mm
The one that I have is 16.7mm.
Any ideas on what this insert is so that I can try to get another?

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