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Getting Exhaust Manifold Bolts Off

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  • Getting Exhaust Manifold Bolts Off

    We have had several good threads on this board about getting out bolts broken into blocks. I am wrestling today with several exhaust manifold bolts that just won't budge and I really don't want to break them off. These are bolts, not nuts so you can't spray them with penetrating oil. I've put all the force on them I dare to using a six point socket and my 1/2" breaker bar. i was even thinking of welding a few blobs of metal on top of the bolt tops (not the flats) just to heat them up a bit.

    Anyone got any good secrets for getting them out without breaking them?
    Lincoln 175HD
    Miller Thunderbolt AC/DC
    Smith AW1, Dillon (Henrob) Mark III & Smith Quickbraze Little Torch

  • #2
    From my experience, heat and impact usually do the most good if the hardware is going to come out at all.

    If you heat the manifold - not the bolt, and then use penetrant, the fluid will wick into any space and offer the most utility it can. Rapping on the head of the bolt with a firm smack while it is hot can aid in getting the penetrant in.

    I have heard some folks have had success using wax instead of penetrant, but I have never tried this.

    I have also drilled the heads of the bolts off and then removed the manifold, leaving studs. The application of heat is a bit easier and the stud can be gripped with ViseGrips, a pipe wrench or a stud extractor. Of course, getting a drill into position is nearly impossible if the engine is still in the vehicle, unless it is a boat you are working on. Cutting the head off relieves the tension and sometimes this is almost enough to allow them to be extracted without too much effort, but they are rarely easy!

    Last edited by MXtras; 10-03-2007, 03:59 PM. Reason: added some more useless ramble
    American Made

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    • #3
      If you've got oxy/act, heat one up to 'bright red', then it'll come out 90% of the time. If not, have your candle (not a votive) handy, and start dripping hot candle wax onto the area where the bolt meets the manifold. keep it up while the bolt cools. It migrates. Then, start smacking the head with a 3# sledge. Don't have oxy/act??? Try MAPP. You Can use penetrating oil (NOT WD_40!)on a bolt, but not right now, because you ARE going to wrench that puppy right out when it cools with the wax in there.

      ...If you are dealing with an aluminum head, heat it, bot the bolt, and don't try to get it red!!!
      "Good Enough Never Is"


      • #4
        Also try going both ways with it. Sometimes trying to tighten it a bit or rocking it back and forth works. And sometimes ya just gotta bust 'em off.....


        • #5
          Sometimes I take an air chisel with a pointed bit and drive it straight into the center of the bolt head, if I can get at it straight on. It helps loosen things up. I also like to try to get an impact gun on it and try to rock it back and forth with low power. A little heat helps sometimes. When all else fails, brute force impact power will either take it out or break it.


          • #6
            I have had alot of luck with just cutting the heads off "however you can" and then just removing the headers, or manafolds. At that point you usually have more room to play.If you break them off 99% of the time they are going to break off flush with the head.Thats no fun when you have to go to the easy outs, break that and its off to the mach. shop. After you remove the header, or whatever you can get the PB Blaster and some good vicegrips on the job. Usually after the tenson is removed and some good soaking they will come out.


            • #7
              Sound advise so far.... only thing I'll add is if you had an oil leak and the area is saturated with oil penitrating oil isn't going to help much (thanks for that info vise grip)... and if they snap off flush torch 'em out.
              George W. Bush saving your butt whether you like it or not!
              If there must be trouble let it be in my day, that my child may have peace.
              Thomas Paine
              Fear is temporary, regret is forever
              HH210 w S.G.
              Victor/Uniweld O/P
              Dewalt Chop Saw


              • #8
                Thanks for the tips guys. I have neither an impact wrench, nor an O/A torch (yet), and since the engine is still in, it was pretty hard to get a sledge hammer in there. I finally got them all out without breaking any by being patient and hammering on them as much as I could with a socket on the end of an extension and a few chisel shots in the middle of the bolt head where I had some clearance through the wheel well.

                These were 9/16" bolts but years of rust and heat and garage monkeys meant they weren't in the best of condition. Fortunately the heads had been off before, judging by the fact that this is a 454 truck motor with passenger car heads on it. Some of the bolts were barely hand tight and others were frozen solid. I ended up using a deep walled 14mm impact socket on my breaker bar to free them up, rocking them back and forth a bit as you guys advised. The 14mm is just a smidgen smaller than a 9/16 so it works well on 9/16" bolt heads that have seen better days.

                Hopefully this motor is coming out the access hatch today using the modified engine crane I welded up with my HH 140. I'll post some pics of the crane mods later.

                I probably should have used it as an excuse to buy an O/A rig, but I resisted the temptation.

                Thanks again.
                Last edited by smyrna5; 10-04-2007, 08:45 AM.
                Lincoln 175HD
                Miller Thunderbolt AC/DC
                Smith AW1, Dillon (Henrob) Mark III & Smith Quickbraze Little Torch


                • #9
                  Yep all you need is heat, oil and vibration. I had a customer come in with broken intake manifold studs, out came the welder...

                  Conrad Andres
                  Thermal Arc 185TSW
                  Lincoln SP135T


                  • #10
                    What is that engine in?
                    "Good Enough Never Is"


                    • #11
                      Originally posted by Hotfoot View Post
                      What is that engine in?
                      Sorry Hotfoot, I didn't see your question before. My engine is in a 1985 Revcon Motorhome I am restoring. Its an all aluminum front wheel drive beast built by a company started by the grandson of the founder of Airstream. My adventures rebuilding it are detailed here:

                      --> My Revcon Restoration Project

                      By the way the last picture in the transmission section shows the latest addition to my bed frame rolling cart project, which my HH 140 did the deed on. I found a steel fireplace grate at my local thrift store for a few bucks, and my mind said, "That's not a fireplace grate - that's a bottom for my parts cart." It fit my cart like a glove! I think next I will add some steering, since picking up the front to change directions gets to be a pain. It still beats carrying heavy parts 50 yards from my backyard to my driveway though. You might say the cart is still evolving as the need arises

                      -->Latest Addition to My Bed Frame Cart
                      Last edited by smyrna5; 10-12-2007, 07:54 AM.
                      Lincoln 175HD
                      Miller Thunderbolt AC/DC
                      Smith AW1, Dillon (Henrob) Mark III & Smith Quickbraze Little Torch


                      • #12
                        Well, the bolts are already out, so that problem is solved.
                        Nevertheless:cast iron exhaust manifolds tend to shrink over time. On a Jeep I-6 engine (258 cid) I was able to find a 1/4" difference between the removed manifold and the engine head, measured between the outer bolts, after removal of the manifold. This creates an enormous force / friction to the side of the bolts. Usually the inner bolts come out easier, but removing them first just because you can do so makes things worse for the outer bolts. So the outer ones must be removed first!

                        Before reinstalling the old manifold, check the holes and enlarge if necessary.

                        If the only tool you have is a hammer, every problem looks like a nail.

                        Fronius Vario-Star 304 (Mig, 400v/3-phase, watercooled)
                        Cemont SX 350S (Stick & DC Tig, 400v/3-phase inverter)
                        Cemont SX 135 (Stick, 230v/single phase inverter)
                        Cebora Plasma Sound 35PC (230v/single phase inverter)


                        • #13
                          A MAPP/Oxgegen setup from home depot can be a fair subsitute for a oxy acetlene rig, it only costs $50 compared to about $250 for a good oxy acetlene. If you have a compressor consider geting a good impact wrench from Ingorsla Rand or Chicago Pumatic for about $150 to $200. You will probly want about 350 to 400 foot pounds of torque. I broke a stud off a s10 with an old Chicago Phumatic a couple years ago. Not sure how much torque it has.
                          Old Airco 180 amp A.C.


                          • #14
                            Since most of my work is big yellow heavy equipment a lot of the bolts will just snap off. Or so the mechs say. I always tell them to tighten a bit first with the impact then go remove. They like to just go reverse right away and let the impact hammer till its out or snaps. These are the 1/2 to 1 in bolt range. For those broken below the surface, Sometimes transfer punch them, drill with bit for threads and retap the hole. Glad you got them all out.


                            • #15
                              Cut the heads off with a torch too.