Broken and stuck c-15 acert exhaust manifold stud help!!!!

Soak them good with penetrating oil. You might tap them with a hammer to break any rust/corrosion. Once you get that initial break loose they should come out easier.

Is there any bolt left? If so use vise grips as close as you can to the base and as tight as you squeeze them.

If they are broke flush then it's drill and easy out. Use a center punch to start the drill hole.There is nothing easy about it.

Make sure you chase the threads when you do get them out.

 

You can get a proper tool to guide your drill bit. Very rarely you have to drill the whole thing out. Usually a smaller drill and an easy/out works well.

 

A left handed cut drill bit sometimes does the trick, Don't use heat until you have to, there is enough carbon in those studs to really harden them and then you need a carbide drill bit......... NOT a lot of fun
The drill guide in morehp's reply along with a left hand bit and the advice is the earlier posts should work well.

 

I've drilled them out several times always with a hand drill and a regular bit. The hardest part is getting a good start as the stud can be slightly below the surface and broke off at an angle. Getting the bit to start without walking can test your sanity. drill the stud all the way through there is a small gap between it and the head so you can feel it push through. Once it's drilled you can get penetrating oil to the back side of the stud which helps. Then use and an easy out. DONT BREAK THE EASY OUT!!!!
That's if they are broke just went back and read your post again. If they are not broke remember the factory torque on the studs is 28ft lbs if I remember correct so they will be hard to turn out.
I would never install them and torque them that high.

 

I always get them out by welding a nut to the stud even if there flush. Arc welder seems to work best.

 

Monaco tool sells that jig that Morehp posted a pic of, with a special diamond bit drilling studs even at the back of the head is super easy. I've also done gearhead's trick except I weld a washer instead of a nut first, then weld the nut to the washer on the outside of the nut. Welding inside of a 3/8" nut and getting good adhesion to the stud vs using a washer first works much better.

 

Steady pressure and vibration is the key. Use box end wrench on nut, air hammer with blount tip bit. apply steady pressure on wrench while vibrating the end with hammer.