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  • Welding a header/cross pipe

    The cross pipe the leads my exhaust into my turbo on my '87 GN has a crack at the flange. (see pic) is there a preferred way to weld this up. I have a MM175 that I was going to use but I could Tig it at work if need be. Is the heating/cooling that goes on that big of a factor? expansion/contraction? If not then I will just Mig it. What about brazing? I've never brazed before, but it seems as though its used quite offen in the bicycle world. should I weld it from the inside out the outside? Thanks for the info and for putting up with my lame beginner questions.
    Attached Files
    MM175

    "Live for Today. Yesterday is Gone and Tomorrow May Never Come" -unknown

  • #2
    Can you post the pics as non-zipped?

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    • #3
      If you save them as .jpg they won't need to be zipped.

      That looks like sheet steel to me, I'm a little surprised they would use that on the exhast side of a turbo. It also looks a little rusty and thin. The crack looks like a brittle fracture, so a weld will only last a short time before it cracks again in the HAZ.

      It looks like some sort of ball flange to accomidate misalignment of the pipes. Would you have to grind the weld smooth to allow the joint to seal again? Seems to me that is a part they would have in an exhast shop. Even if you get a replacement flange that is for a differnt type of car, it would be preferred to replace the whole thing and put the weld somewhere else.

      As far as weld type, (assuming it's steel) you are best off welding with whatever you have more experince on. Be careful to clean the base metal, and avoid the fumes if it was or is galvanized or plated.

      Sorry but that's the best answer I can give.

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      • #4
        INTP: below are the pics in jpeg format. thanks for the info.

        Eric75: I would have to grind the weld smooth. after you mentioning that I could have problems with it in the future, I found a new SS one for sale online- only $80. So I bought that. I will still weld this one up for the practice, but a little crack like this robs me of a couple pounds of boost, and I don't want anymore problems. Thanks for you help.
        IBRAILN
        Attached Files
        MM175

        "Live for Today. Yesterday is Gone and Tomorrow May Never Come" -unknown

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        • #5
          After seeing the closeup I would tig it with SS filler. Just my .02, for $80 in SS I would have replaced it also!

          Peace,

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          • #6
            be VERY careful of crap going into the turbo. Friend had a very small leak in his header tube and put a very small mig weld tak on it and some how a little mig filler went into his turbo vanes and made a mess.
            pakmanmotorsports.net

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            • #7
              I suggest trying to track down the reason for the crack in the first place. Even with the new SS piece, the problem could come back if there's some other root cause. My guess (since it's a turbo piece) that it has to do with heat cycling and no accomodation for expansion/contraction.

              You might also consider a thicker piece as a replacement.

              good luck.

              Comment


              • #8
                PAKMAN, INTP-
                I will do both of your suggestions. The one I'm welding will be a spare piece now that I ordered a SS one. However I will still keep this in mind.

                INTP-
                I'm guessing the that the crack was cause by the expansion/contraction over time. The car is an '87, so I believe that time took its toll. Since you brought this to my attention though, to look for a root cause, before I install the new pipe I will double check all my other bolts to be sure they are tight. A little vibration could cause one heck of a problem.

                Thanks everyone for you input.

                IBRAILN
                Attached Files
                MM175

                "Live for Today. Yesterday is Gone and Tomorrow May Never Come" -unknown

                Comment


                • #9
                  Sweet Car, You are correct in checking your fasteners. I was going to chime in earlier & got a phone call (dam job). Expansion possible, Vibration possible, combination of both and add a little time, 15 years definate. I have seen this exact devolopement with a unit on a turbo housing, diesel engine. the only true fix was 2 additional supports not engineered from the factory but the attachment locations were present. I am sure the engineers at GM did not expect your car to still be in service and looking that GOOD .
                  Good luck and my your problem go away.
                  Laurence

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                  • #10
                    hummmm a grand nat at the cop shop ??

                    who was going 110mph in a 25 ?

                    ha !

                    dawg

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                    • #11
                      Yeah that was a good weekend. the car did right around 11.14 in the 1/4 mile, in Vegas. I would have to find the slip for the exact time, but it was right around there.... No trailer, Drove it from San Diego to Vegas, and most importantly- back home...
                      MM175

                      "Live for Today. Yesterday is Gone and Tomorrow May Never Come" -unknown

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                      • #12
                        Sweet car!! Grand Nationals have always been a favorite of mine! Unfortunately, in my area they are hard to come by and if you do find one, they were pretty much abused by people that didn't know what they had

                        As for your problem, the factory crosspipe on GN's have always been a problem area for many reasons especially as they get older. Since the crosspipe comes in direct contact with the turbos, my suggestion would be to replace it and the downpiping with a SS piece and make a good inspection of the headers. They have also been starting to crack at the flange as they age. If all is well I would think about installing a turbo timer in the car. This is a device that determines how hard your car has been running by the o2 content in the catalytic converter and when you go to shut off your vehicle it will keep your car running for a determined amount of time in order to keep the flow of oil running through your turbos to cool them down slowly. It also keeps the oil from coking inside the cooling passages of the turbo.

                        Of course if you wanted a serious project, you could fab up your own headers, pipe in one BIG turbo(like say a PT76!) and start having some serious fun
                        MillerMatic 210, ThermalArc 185, O/A Victor outfit

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                        • #13
                          If you tig it, it will have to be cleaned very well. And with all the exhaust gasses and corrosion there already, you may find tig will contaminate from the backside and crack again. Sometimes it's best to just go and use the softer mig wire and put it back together. The SS exhaust on my turbo 350 dually was all mig welded and no cracks yet. I think you'll find that no matter what you do, the base material has been stressed to it's expendable life point and any repair will be a temp fix.

                          Good luck!

                          Andy

                          ps
                          cool car

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