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Old 08-13-2008, 09:20 PM   #1
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Default Broken exhaust manifold bolts

Has anyone removed broken exhaust manifold bolts from the head while on the car? The front and back bolts are broken off flush with the head on the drivers side(I thought the front one was just missing when I bought the car and saw the back one was missing when I replaced the clutch 2 weeks ago. Last week suddenly the car starts sounding like the rockers haven't been tightened down and I'm thinking exhaust manifold gasket leak. So when I took a mirror to look in the bolt hole, I could see the broken bolts Any suggestions? And why would they break in the first place?
Stock exhaust manifolds and stock exhaust sytem, all hangers and rubber mounts in excellent condition
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Old 08-13-2008, 09:29 PM   #2
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A simple solution would be to get some headers. Headers don't use the very first bolt hole or the very last bolt hole in the head. This honestly would be your best bet for trying to get out broken bolts is semi a PITA enough, but removing broken bolts with the head on the car...ouch.
 
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Old 08-13-2008, 09:29 PM   #3
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How good are you with a small right angle drill, a tap, and a helicoil?
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Old 08-13-2008, 11:43 PM   #4
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Originally Posted by ShowNoMercy View Post
How good are you with a small right angle drill, a tap, and a helicoil?
Probably not as good as he needs to be.

As hard as bolts are to drill out in the first place, I don't think I would even try it with the head on the car.
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Old 08-14-2008, 02:29 AM   #5
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Default A possible fix fro broken LT1/LT4 exhaust bolts

Go to a muffler shop or friend with a good welding skill set, place a steel washer over the hole where the broken bolt is, weld the center/internal edge of the washer to the broken bolt end (just a small weld and avoid the manifold inner edges). Next weld an old/short bolt to the center/outer edges of the washer, no need to be perfect just a healthy weld. While still hot from the weld, place your socket on the temp bolt head & out is comes. Find some Flanged grade 8 replacement bolts and never have to do this again. If you are real concerned even after all of the above, or you are into overkill, get Stainless Steel Grade Nine Flanged bolts and this set up will outlast us all!! No need to get headers unless you are into those mods/have the extra money/need the added HP.

The reason for them braking: GM used Grade 5 bolts and with the normal "elongation" response of these bolts, the heat soaking cycles and time causes metal fatigue. Bolts will show more elongation characteristics than say screwed in studs. When we use studs, the torque & twist loads that are on the none threaded & outer threaded areas of the studs and are only seen when the assy is tightened with header/manifold in place. Therefore, the studs do not get subjected to being screwed into the head under loads. With regular bolts, the torque loads are seen as the bolt engages/rotates into the head material. Therefore, lower grade bolts tend to start out weaker by the nature of the threading-in/torque loading process & where the thread pitch diameter has changed/been altered at the thread ending (a natural weak point). Again, Flange Grade 8 bolts are strong enough to overcome this issue on 99% of our stock applications. Good Luck! :-)

Last edited by LT4_TA; 08-14-2008 at 03:52 AM. Reason: Clarification
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Old 08-14-2008, 09:03 AM   #6
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Good possible solution, but getting to the back bolt hole to weld anything is going to be a real trick.
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Old 08-14-2008, 11:34 AM   #7
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As shoebox already said, The rearmost bolt hole is impossible to get to. I had the same problem on my old heads, and there is no way in hell to get to it. Even a right hand drill is too big to get in there, a welder nozzle is the same, go forbid you start laying beads on the aluminum head with a MIG because you cant quite reach, and then start warping and cracking s***.
Either do what CKJ suggested with the headers, or pull off the heads and have them done by a competent machine shop. You cant really band aid this one
Good luck
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Old 08-14-2008, 01:06 PM   #8
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Default Clarification

All of the above points are well taken. If your bolt is broken between the outer edge of the manifold and about mid way in toward the head surface, you still have a chance to remove the broken bolt without exhaust & or head removal. Most GM LT1 OE exhaust bolts will break where the threaded portion stops as you move toward the bolt head (again the weakest point). Therefore the possibility of the bolt breaking in the head or near the head surface is not likely. Since this has happened to me on my B-Body & one of my F-Body's, I was able to have this done at a local muffler shop with a MIG welder. The B-Body took all of 8 minutes to remove the broken bolt. The F-Body will be the most difficult to possibly fix. In my case, the welder used a small angled tip, wire fed MIG welder (made by Lincoln I think) and was able to get it done in about 25 minutes on the pass side. The driver exhaust cat with Y-assy & pass connection will need to be removed if you have an ODB2 set up, since all of this is done from the bottom. The wire feeding was perfect to create the fill needed to connect the bolt to the washer. When welding onto the stud with the stock manifold still on, there is very little chance of overheating the aluminum head since the weld heat/saturation period is only about 10-12 seconds to connect the washer and about the same for doing the temp bolt to washer weld...... The OEM LT1 cast iron exhaust manifold will not take a low energy MIG weld so the only media left is the broken stud. This can be done if you find a shop that has the small tips and the skill.

I only give this out as a possible fix when a person does not want to remove the head. If the broken bolt is not broken in the head (nearly impossible) or near the head surface (a rare thing), and you remove the manifold you still can use this method. The removal of the exhaust manifold will expose the broken bolt & you should have enough room to use the weld method.
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Last edited by LT4_TA; 08-14-2008 at 01:08 PM.
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Old 08-14-2008, 02:40 PM   #9
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^^ Good points!
I realise some might have a chance if there is a bit of the bolt sticking out, but as the o/p stated, his are broken off flush with the head, and are the rear most, as was my case as well. I think me and him must be the 2 unluckiest bastards out there if these bolts "rarely" break off flush with the head. Obviously this is the case here.
I am a welder, and for the life of me could not get near the rear pass/side bolts on my old heads. Then again my hands are "ham fists"
Good luck in either case.
Maybe consulting with a good exhaust shop might help him out.
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Old 08-14-2008, 03:19 PM   #10
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I do recall a buddy working on his LT1 and deciding to remove the spacer & use a shorter bolt when the original bolt & spacer fell out. When the short bolt is used, the break will be nearly flush to the head.... good reminder! If the manifold is off, a good welder should still be able to use the washer method and avoid head damage. Note: The washer ID must be smaller than the bolt OD so there is no head material exposed to the weld bead.
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Old 08-19-2008, 02:56 PM   #11
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Got the exhaust manifold off and I have 3 broken bolts. Front and back are broken off flush with head. Second from back broken off 2 threads in. I have tried the weld method many times before, just a little nervous with the aluminum heads. I usually build out the weld on the stud and then weld a nut on the buildup. The weld has the benefit of shrinking the steel in the stud when it cools, allowing the stud to release from the surrounding material
BTW, I think the cause was a broken motor mount on drivers side. Time for a set of Polyurethane as the drivers side OEM is $220.00
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Old 08-19-2008, 03:26 PM   #12
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If the bolt protrudes a bit, then you could try what I did. It's similar to what LT4 TA suggested, I found a nut that fits over the stud and then welded it from the stud to the inside of the nut, filing it as much as possible making sure I didn't touch anything else, not even the outer edge of the nut itself; of course I had enough room to do this.
Good luck!
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Old 08-25-2008, 09:22 PM   #13
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Yeeha, got the little buggers out. Here are some pics, the ones of the broken bolts before I started didn't turn out. Sprayed the head with spatter release, then cleaned the broken stud. Welded a bead on the stud and built it out, then welded on the nut. Took about 2 hours.
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Old 08-25-2008, 10:03 PM   #14
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Quote:
Originally Posted by HiTempguy View Post
Yeeha, got the little buggers out. Here are some pics, the ones of the broken bolts before I started didn't turn out. Sprayed the head with spatter release, then cleaned the broken stud. Welded a bead on the stud and built it out, then welded on the nut. Took about 2 hours.
Glad to see this method worked, thats been the way I've done it for years.
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Old 07-31-2010, 08:50 PM   #15
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i just recently got a 1994 firebird 5.7 and have found out that the manifold bolt closest to the driver is broke and the one next to it, they are broke off somewhere in the middle of the bolt. i dont know how to work on cars and really know nothing about them. all i know is its fast lol. whats a reasonable price a shop would give me, after looking at these post i dont think the backyard mechanics that i know will be able to fix. any info would help thanks
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