What I called a sleeve is the same thing as the adapter just bad terminology on my part.
At some time in the past my car had the head replaced with one from an earlier model.
It has an adapter on one of the plugs.
It has leaked in the past as someone used a bunch of RTV on it to stop the leak from the valve cover o-ring.
The first time I tried to change this plug the adapter came out with it. The brass from the adapter had fused itself to the sparkplug and so far I haven't been able to get it off.
This adapter is not a helicoil it is a brass sleeve with threads inside for the plug and cutting threads on the outside. It almost looks like a tap on the outside and is larger than a bigger sparkplug.
I am going the change the valve cover gasket and o-rings this weekend and will see if I can do anything to salvage it.
I will shoot a picture of the sleeve too, it actually has the spark plug number stamped into it.
