Greetings.

I've recently changed the valve cover gasket on this car which had cracked and found the spark plugs on 3 and 4 swimming. I know about the problem regarding the washers leaking onto the valve cover, but after fully drying the head, plugs and leads, this car ran like a sewing machine for 5 or so minutes then started to misfire. I removed No.3 lead and found water in this side again. It does look as though the core plug is leaking. Are these normal press fit core plugs or are they threaded?

Any help would be greatly appreciated