Exhaust stud replacement

While dismantling my t4 I sheered the very end of an exhaust manifold stud off. I need to replace it. Do the studs screw into the head or do I need to grind it flat, drill it and tap it. ( the head is now off so access is easier). If it is screwed in I can grind some flats onto it and use a toolmakers clamp to get a grip and unscrew it.
Any advice or suggestions appreciated

 

Unscrews, is there enough left to lock a couple of nuts on it?

 

Or good old molegrips of course...
Whichever, turn it to and fro with a small amount of pressure and eventully it'll loosen. Don't wang it full strength or you may strip the threads and need a helicoil.

 

Not enough thread but cheers for the answer. I've got the kit to unscrew the mother nuts on the Death Star but didn't want to do any damage.

 

I have the same problem and been told that if its an original head, the chance of getting the stud out is less than 50/50 ( a lot less ! ).
However, if they are repro heads ( mine are AMC ) then it should come out as they are not fitted at the factory, but came lose with head.

 

If anyone has scrapped heads because of broken studs, ill take them off your hands!
Especially 1800 ones.

 

Didn't realise studs were different size treads at each end. Going to order some from coolair today. Was going to use some threaded bar like I did on my t1 motor but obviously can't.

 

I had to get my head cut open and welded back up in order to remove a seized exhaust stud....very annoying!

 

It sheered off close to the head after turning 1.5 turns so now have to drill it and tap it. More work. Fortunately my dad is a retired toolmaker so skills and tools are available.

 

I sheared a couple and had a knackered thread on mine, older heads have an m8 stud all the way through, newer heads are m9 in the head and an m8 stud sticking out.

Having older heads is quite handy when you've got a knackered thread as you can just drill and tap it up to M9

 

The M9 thread is just the right size to carefully tap for an M8 helicoil if you have the kit.

 

Bit drastic, wasn't it ?

 

I'll let the toolmaker loose to drill it out. He'll do it accurately with a pilot to relieve pressure on thread then a stud extractor or left handed drill bit to get the remains out. Setting up to drill straight is the key I think and getting the drill bang on centre.

 

I'll drill it and retap. Small stud extractors invariably snap

 

Drilled, retapped new stud screwed in. Not too bad a job. Head going back on soon.