I have just done this job yesterday on my 2.2 petrol ...it was the very front lower stud that had been sheared off prior to me owning the car. I was able to drill it (1/8th) and remove it with my mates Snap On stud extractors once I had removed the manifold, oil dipstick and thermostat housing. I used new studs, gasket and nuts but put the studs into the head dry.....what its the "anti seize compound" that JamesV6 refers to??? the new studs were bright silver as aposed to the old ones which were black....i thought this was a plating (possibly zinc?) to stop internal corrosion.
Id be interested to hear how you did this in detail as ive got both the top and bottom studs snapped on no1 cylinder......was the stud snapped off inside the cylinder head? (mine are)
Sorry for the delay in replying TD.....We use a 1/8 cobalt drill bit in the end...others were just being blunted. My stud was sheard off about 1.5mm inside the head. Access to get a drill in is tight so i used a small air driven grinder with a small chuck inserted similar to this one
http://cgi.ebay.co.uk/1-4-NEW-PRO-AIR-ANGLE-DIE-GRINDER-AIRCRAFT-TOOLS-F49_W0QQitemZ290163008273QQihZ019QQcategoryZ22664QQcmdZViewItemI used a new stud to guage how much thread was left in the head and just kept checking the depth....drill too far = knackered head!!!
There really isnt that much stud in the head so i doubt if a normal easy out would have sufficient to grip on to to work.
The stud extractors we used were a set of these
http://cgi.ebay.co.uk/SNAP-ON-BLUE-POINT-SCREW-EXTRACTORS-NO-RESERVE_W0QQitemZ170150717599QQihZ007QQcategoryZ30917QQssPageNameZWDVWQQrdZ1QQcmdZViewItemwhich again I was lucky enough to borrow.They really are the muts nuts.
The important thing is to get the hole drilled in the middle of the sheard stud....the extractors come with a sleeve that slides over the drill bit and is just the right size to nestle in that hole in your head
that your stud is broken off in. So in this case I was lucky that my stud had not broken off flush but was slightly sunk in
The other important thing to get right is to keep the hole running at 90 degrees to the head. The extractor is then hammered in (they are a straight rod with straight splines that grip the stud when hammered in) and the stud is screwed out useing a special nut adaptor that slides over the extractor splines.
I had soaked the stud with copious amounts of plus gas overnight which may have helped and I was lucky...my stud came out.
Why the studs shear I dont know...none of them were really tight, eight of the remaining nine came out with the nuts when I removed the manifold and as I said the sheared off one was not as tight in as I thought it would be....I get he feeling that maybe it had just fractured and fallen out possibly due to a warped manifold. There must be an explanation as its always the front studs that go.
The alternative is to get the head off and do it on the bench which would be easier but a lot more time consuming and expensive and there is always the possibility of something else going wrong during the head removal/replacement.
I did this at the start of a week off work so I would have had time to go down that route if it had all gone wrong.
Hope this helps TD and if you want any more details just ask