There's probably some kind of goop out there, however;
I'm not sure if the Iron heads have a slightly tapered port (like I think the Alloy heads do?), but might be worth checking the end of the pipe where it goes into the head and check its condition ie;
Ones I've had were a bit of a sloppy fit (actually partly 'rounded' at the port ends), so I stretched it slightly to make it parallel and a touch bigger than the inside of the port, so when it's pushed in becomes a nice snug fit, but add a very slight taper (or file the hard corner off) at the very end, so it doesn't gouge the port material-
Hope that makes sense...?
To do it I used a bit of 1,3/8" x 1/16 wall tube should be a snug fit inside the 1,1/2".
Cut some slots up the length of it a half inch or so and stuff it in....but you need to be able to get it out, so I had a washer the right size to put in first with a bolt through it....and maybe more...if I remember more, I'll let you know if need be...I' sure you just want a quick fix, but good luck
