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Repairing an Exhaust Manifold

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  • Repairing an Exhaust Manifold

    Well I finished this project back in September, but I guess better late than never.

    I posted several questions here regarding the project and thought I'd post an update.

    So here it is -

    I needed to repair a severely damaged cast iron exhaust manifold from an old International 350 tractor. This is how it started:

    At some point, someone else tried to repair it with a "bubble-gum" weld.

    It was also concave by about 0.020"

    The first thing to do was clean it. I started off by degreasing it with Simple Green, followed by wire brushing the whole thing with a SS brush.

    Last edited by Fasttrack; 07-11-2013, 01:50 PM.

  • #2
    After cleaning, some other cracks became evident. In order to prevent the cracks from continuing to propogate, I drilled holes at the ends of the crack.

    Here someone else tried repairing with braze. Not a bad choice, but CI does have low wetability. Here you can see that the low wetability really caused some problems for the repair guy.

    Here it is cleaned and bolted to a simple fixture to keep everything in alignment.

    Last edited by Fasttrack; 11-29-2010, 09:49 PM.


    • #3
      To remove the carbon deposits, I etched the casting in muriatic acid.

      After the acid etch, it got washed in a solution of baking soda and water to neutralize the acid and prevent rust. I then hit it with the SS brush again and then it got a serious soaking and scrubbing in acetone.

      Then it was time for the pre-heat. The oven goes to 600* F ... just about right.

      Last edited by Fasttrack; 11-29-2010, 09:52 PM.


      • #4
        Here is the casting after being heated. I used "Peterson #2 High Heat Flux for Cast Iron". Frankly, I was not impressed. I ended up using ordinary flux for some of the minor crack repairs because it could be mixed into a paste and was just easier to deal with.

        I should also add that I used a carbide bur to groove the cracks prior to brazing.

        I also had to blow out some broken studs, but I damaged the threads in the process. I ended up machining some bungs and brazing them in place.

        After I finished brazing, the casting was heated up to 600* F and then allowed to cool over a period of 24 hours.

        Here I am machining the gasket surface flat again. Notice I'm using a solid carbide 3/4" endmill. I tried it first with a flycutter but even on the slowest speed I was dulling the cutter in no time flat. It wasn't too surprising - most castings end up with hard skin of something akin to white cast iron, it seems.

        Last edited by Fasttrack; 11-30-2010, 03:22 AM.


        • #5
          Here it is afterwards:

          Another shot:

          Then I painted it with some $$$ Por-15 high heat "Black Velvet" paint.

          Overall, it turned out pretty well. That Black Velvet paint really is good stuff - way better than the rattle can stuff that seems to turn to powder and wipe off on your hands.
          Last edited by Fasttrack; 11-29-2010, 10:07 PM.


          • #6
            Fantastic job Fasttrack!

            And it looks like it was a job too!

            Going to do a look see on the "Por-15 high heat "Black Velvet"
            May be just what is needed.


            • #7
              Nice job and welding manifolds is always a tricky job and time consuming if done right.
              It's only ink and paper


              • #8
                Well I like to think I did it right, but regardless it was definitely time consuming!


                • #9
                  Looks great. These repairs are very interesting to me, since I own a few old tractors. Thanks for taking the time and effort to post pics and give us a description of your process.
                  Location: Saskatoon, Saskatchewan, Canada


                  • #10
                    Great job Fasttrack! Having done a number of them myself you certainly did do it the right way. It is VERY time consuming to repair any cast iron properly.

                    I will say, you can get away with 400-450F for preheat, if you have enough torch to keep it hot. Or as I do, put it on a propane grill or heating pot, and keep it hot while you are working. I do repair certain "issues" with cast iron blocks for race engines. Never had a failure yet. However, with heads and blocks, I pick my battles carefully.

                    Glad to see someone doing quality work!


                    • #11
                      Originally posted by Fasttrack
                      I needed to repair a severely damaged cast iron exhaust manifold from an old International 350 tractor. This is how it started:

                      Holy cow!

                      I wouldn't call that severely damaged. I call that bringing it back from the dead!

                      Impressive work. Kudo's.


                      • #12
                        Thanks for all the kind words, folks. I think if it had been mine I would've been tempted to find a junkyard replacement or make a header out of steel pipe, but it belonged to my lady-friend's father. There is a very high probability that he will be my father-in-law in the near future, so I figured before I talked to him about his daughter I better soften him up by fixing his exhaust manifold.

                        I'll keep the temperature advice in mind. I recall reading somewhere that 600* was when a phase transition occured in cast iron and that 600* was the proper temperature for annealing but I wasn't sure what temp would be good for a pre-heat.


                        • #13
                          Very nice job. Whole 9 yards done to it, Real improvement!

                          Only thing I wonder about when flatening down mating surfaces...
                          Is the motor side flat or convex?
                          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                          • #14
                            My oven only goes to 500 so that is what I use all the time and everything so far has come out good. There was one mitsubishi 4 spider differential that didn't want to take weld for some reason but after lots of work it held and never broke in the car. I have yet to get excited about welding cast, its not my favorite job in the shop.

                            Very nice job on the mani! I too would have made up the jig and thrown the mani out and built a tube header and intake.


                            • #15
                              Indeed, a nice job and good writeup.

                              Civil engineers build targets, Mechanical engineers build weapons.