Oil leak …

[Gnasher]

There should be no oil coming out of there. Sounds like someone has drilled out a stud and got it wrong.

:agree

Sounds like someone has drilled the stud hole deeper due to it being stripped, seen this a good few times. :rolleyes

If it's the top stud hole that's leaking they likely penetrated into the camshaft space/well if it's the lower possibly an oil return gallery.  Pop off the cam cover and take a look, if it's the former you'll see the hole/bolt in the cam well it's only has to be tiny for it to leak.  If it is and the thread in the stud hole is good it's just a simple matter of sealing in a bolt/stud.  If the current bolt is good and long enough you should to be able to cut the head off and make a stud out of it, if not get one you can.  With either with the current or new bolt that is long enough, to reach the bottom of the stub hole and protrude enough to accommodate the exhaust header collar and nut. Check all that first before moving to the next bit.

Now clean the stud hole front/back and around the area inside the cam well, with brake cleaner to remove all traces of oil.  You might have to use some blue tack positioned above/around the hole like a dam to stop oil running down and back in the hole.  Using stud lock not nut lock, stud lock is normally green if you can get Loctite 270, they do 10ml bottles, which you can get off fleebay or amazon for about £10 inc postage or less.  With the stud hole oil free (give it another blast of brake cleaner, allow it to dry off, now liberally coat the bolt and inside the stud hole with the stud lock and insert and bottom out the bolt in the stud hole. Look for some of the stud lock oozing out of the hole in the cam well.  Make sure the hole stays filled again you may need some blue tack under/around the hole to keep it there.   

Leave it for about 3-4 hrs, job done   

If it's the lower stud then you'll just have to clean out the hole, be careful when spraying the stud hole with brake cleaner as is will end up in the sump.  I would recommend you cover the bolt in the cleaner and quickly insert and bottom it several times until the bolt comes out dry.  On the last and dry extraction, more cleaner on the bolt and put it back in, while you get the stub lock out etc.  Remove it coat it and insert it as fast as you can, this will limit the amount of oil that gets back in the stub hole. 

Make sure you clean all the remaining studs of corrosion, use proper anti seize paste on all stubs before refitting the exhaust nuts.   

If you ever need to remove the bolt, you'll have to use heat to melt the stud lock.

I've done the above many times.