I successfully removed the broken head stud from the
1.9 L waterboxer I am working on.  It was in there good
and tight so I read the various methods described in
the archives.  Getting a good grip on the stud shaft
is difficult and I don't have a stud removal tool so
I tried welding a nut onto the end of the stud with
my MIG welder.  After a couple of failed attempts to
get strong weld, I found an 11/16 nut with a thread
size somewhat larger than the stud shaft size.  With
more space around the stud I was able to fill that
space with weld and get a good joint.  Then I used my
air impact wrench and it zipped right out.  This was
done with the engine out of the vehicle and on an
engine stand.

 -Dyer Lytle in Tucson