Need help - sheared off exhaust manifold studs

I recently bought a new exhaust system from Chris Roop. In removing the old system (which must have been in place forever!), I ended up shearing off every one of the six lower manifold bolts where the first section of exhaust pipe hooks on.

To make it somewhat easier on replacing, I have taken the time to remove the carbureators, etc. and I now have the exhaust manifold off the engine and on my garage floor. I've ordered six new lower studs but I would now like to hear some suggestions for how is the best way to remove the sheared off studs that are still in place. Some of them are sheared off almost flush while others have a little bit of the bolt still sticking out. I doused everything with penetrating oil last night. Should I be thinking of drilling a small hole and using an "easy-out" or should I simply drill out the entire hole where each stud is left? Also, I have a blow torch - will this do me any good?

Suggestions?!

I soaked, tried ez out, tried ez out with heat, and ended up drilling and retapping.

I've just done this to one of the studs a couple of days ago. Here's a quote from my journal 'bout what happened as I drilled it out.

"The lower two flanges had stainless studs put in them by the PO and the nuts on some of them were binding so I had planned to try to run a die nut over the studs and buy new SS nuts for them.
When I looked closely at the worst of them, I could see that it had a bend in it.
I was able to get it reasonably straight but when I ran the die nut down it, the thread went on an angle and cut too much of the diameter of the stud away.
I bought a 2" SS bolt and some nuts and washers today, cut off the head of the bolt and went about trying to get the damaged stud out.
The manifold, of course, is off the car so access was not an issue but my attempt to unscrew it failed. I tried heat and a pair of vise-grips but was reluctant to get too enthusiastic for fear of cracking or breaking the cast flange.
So I cut it off level, centre punched the middle and drilled it out with a series of drills up to 6.5mm quite successfully.
Thinking I'd be able to cut or displace the remaining threads out I proceeded to use a 5/16 Whit tap to try to clean the thread up.
This proved to be very difficult as the hardness of the SS compared to the CI eventually meant that the 'new' thread ended up being cut into the CI and not removing the old stud thread bits.
I should have realised what was going on when all of a sudden the tap started to cut real easy but it wasn't 'till I was almost through and saw that there was fine particles coming off the tap and not the bits of SS thread, that it dawned on me what was happening.
The new stud would screw in, but it was very loose and I'm sure wouldn't have held under any pressure.
I had some Locktite 660 that I'd used to fix the bearing for the rear axle a few months ago, so I used some of that to fill out the thread.
It's not it's main application but in that position away from most of the heat, it should be OK. If not I'll just have to take it out and do it some other way. I'll worry about that if it happens.
There's not very exciting photos for this but I'll take one tomorrow just in case my explanation is not as clear as I think it is."

Try not to do the same thing. Sorry for the long post.

Chris

I cheated - took it to my local machine shop and had "Helicoils" put in. Use LOTS of "CopaSlip" on the studs so they don't re-rust!

damn, i did the same thing a few days ago.removed 2 broke off one and then just stopped. took it to a machine shop and had them remove them. no problem.

I like to think I'm capable of performing all but the most intricate of tasks in my little shop out back. I can sympathize with you about the studs. I broke one out, and went to replace it (just like every body else here) and wound up with a three day project. I wound up taking my manifold to a cylinder head rebuild shop and having them extract ALL the studs and helicoil the one I broke. While I was at it, I had them do the same to my spare (minus the helicoil). I replaced the original manifold, and within two weeks the helicoil had broken (taking the entire corner off the manifold) and the donut had once again begun to leak. Fortunately for me I had a spare, and was able to swap out in a couple of hours.
This is a recurring problem with our cars, and I have found that EXTRA care must be used in performing what appears to be a very simple task.
Have fun

There is no good way to get the old studs out - but you knew that! :)

If you are very good with a drill, then drill a hole in exactly the center of the stud. You will have to mark the center with a punch in order to start your drill without wandering. Drill a hole big enough to put an Easy-out in and try to back it out. This probably won't work. In that case you will have to drill the whole stud out - without harming the threads (much).

You will almost certainly not get your drill perfectly centered. Drill the hole with successively bigger bits until you are almost through the wall of the stud. Try the Easy-out again - it still won't work but you can tell yourself you tried. Using the smallest possible drill that accomplishes the task, drill a hole that just touches the threads on one side. The stud is now very week. Using a punch and hammer, tap the stud on the thick side - collapsing it towards the center. Once it begins to collapse you can usually get it out with a pair of needle nose pliers. Clean up the threads on the manifold with a tap. If you botch this procedure, do not despair - you can always put in a Helicoil.

Thanks, guys - I'm getting the message. This really sounds like something for the "pros" to take care of. I think I'll opt to take the manifold to a local machine shop and let them do it.

Terry has it pretty well nailed. One thing to keep in mind, though, is that if the stud is broken off flush to the manifold, it's very difficult to see EXACTLY where the center of the stud really is. You're looking at the thread depth on one side of the stud, and the actual outside diameter on the opposite side. This is the reason to start with a smaller drill and work your way up, until you start to see cast iron on one side of the hole.
If there are still a couple of threads sticking out of the hole, you can thread a nut on it and use a tap-size drill to establish center, but once you've done that, I'd still recommend stepping up drill sizes until you see threads; I doubt any of us can drill straight enough to simply go on through with the tap-size drill.
Once in a while, you'll get lucky enough to find the back side of the stud is sub-flush on the other side of the manifold to where you can start a tap-size drill from the back. Often, the stud will screw itself out as you drill. In any case, a large vise is necessary to hold the manifold securely in one place. It really sucks to break a drill off in the hole because the manifold moved!!!

This simple method always works for me. It has to be goof proof as I haven't goofed it up yet!
If you have access to a MIG welder weld a 7/8" flat washer to the broken stud, then weld a 9/16" nut to the washer. With a 9/16" wrench just turn the broken stud out.
The MIG doesn't seem to hurt the cast iron. It super heats the stud tho so it causes it to break free and then it is easier to turn that pesky stud out.

I have had expeirience years ago with broken studs and have gotten them out. But....recently I took my manifold to a machine shop and had all six removed and six new ones installed for $22.50. Drop off on Monday and pick up on Tuesday. Although one can get some satisfaction on doing it your self, I can't imagine doing it at home. My time is valueble also and I considered the $22.50 money well spent.

My 2 cents.

Mike

Also consider having them spark erode the studs out.

Russ

Then there is the heat it up and run wax on it method.

lessons learned: if planni9ng to remove any part of an exhaust system on
engine , plan ahead .. i use CRC 5-56 or 6-56 to soak fasteners. squirt mon,
wed,fri <all fasteners liberally> and sat morning all comes apart without any
problems..if you drive the car daily it still works ,just let eng cool for about
an hour..
if any engine has 60 thou or more miles on it its best to replace all studs/nuts
60 thou miles of heat cycles weakens the material significantly..

This just happened to me. For the manifold/downpipe studs, I ended up drilling them out and re tapping the threads. Then replace with new studs. (I tried MIG welding the nut on but it still wouldn't budge.)

For the one I broke for the manifold/head, I drilled it out and helicoiled it. The helicoil is super strong and easy to do.

Spencer