[GaryC]

Hi Lynn. I'm not completely sure about this statement but I thought I heard/read somewhere that those plugs were installed when the blocks/heads were fresh out of the molds and the plugs were put in cold. Once the blocks/heads cooled they are next to impossible to remove. Someone with more experience will have to add to this. I was trying to remove the plug from my 69 Z intake and found it impossible to remove, so I looked it up online I think, years ago.

Did you remove that plug from your intake without destroying the threads? I never went any further on mine for fear of that. When I was in the Air Force going to school on the B52's we had some deep training on the corrosion aspect of different metals and how they create different kinds of corrosion and the problems they create in structure stability.