[TR] Head Plug

[terryrs at comcast.net]

There is an aluminum plug (Moss #310-035) on top of the head under the rocker.  The Moss diagram shows it slotted and apparently threaded.  Mine is likely original--no slot.  

It's weeping water pretty steadily.  Not a lot, but under pressure and over time too much.  

Question:  can this be removed and replaced while the head is on the engine?  And how does it come out?

Thanks, everyone!

Terry Smith, TR3A  TS 58667
New Hampshire