If you have the exhaust manifolds off I recall that the adapters have a square/flat surface that can be held with a wrench while the tube's nut is then loosened.

With the exhaust in place, these flats on the adapter are not really able to be utilized or seen, for that matter.

Hope this is of service.

You probally already have applied some penetrant ..... but a good practice as well.

 

Yes I have applied penetrant and I've found a small pair of needle nose vice grips to try in those flat spots. May try heating the nuts slightly too...
Will let you guys know how I make out
Thank you for the replies

 

Your Shoes

they won't turn off because whoever did the last gasket change didn't tighten the adapters going to the head enough

Can imagine your frustration. Manual indicates those are internally tightened with a hex bit. If access is available you may have to cut the adapters and replace with new ones if available. Limp wrist install or should have been changed during previous HG change. The WM says use new adapters when doing R&D of head and now I know why it might be a good idea to follow the manual. Good luck and will be interesting to hear how this turns out for you.

......

 

If you can figure out the size of the square backing nut, you can easily get a crow's foot wrench on it. that's if you can get the crow-foot wrench in that size. I couldn't find one locally, although I didn't try the back room at Napa. We were able to get a wrench or pliers on that backing nut with just the right angle and a lot of patience. Stubby wrenches work wonders too. Naturally, plenty of penetrating lubricant beforehand. I didn't remove the exhaust or anything. I tried for an hour but my brother showed up and broke it loose in about 5 minutes, so it can be done. I think I used something like a 1-1/8 or 1-1/4 on the main union nut and the backer is about 19mm.

 

The size is 18mm. If you have a stubby 18mm wrench it will work perfectly behind the secondary air pipes. I always use penetrating oil like PB Blaster and a torch to get things loosened up.