Customs 292 ford inlet manifold help needed

hi all , working on a 1961 galaxie with a exhaust leak in the centre port of the inlet manifold . on the left hand side near the base of the centre port, there is like a mushroom like ****on which has an exhaust leak behind it , anyone have any idea on what this is , and is it removable as in does it unscrews or is it a press fit , and i have to remove the manifold to repair it

 

You will find this thread helpful: http://forums.y-blocksforever.com/Topic103772.aspx

 

that was just the info that i needed , a really simple fix , 10 minutes work when you know how.
thanks for that