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necassary to weld inside of flange joints?

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  • necassary to weld inside of flange joints?

    i make most of my manifolds with mild steel flanges and schedule 10 304ss pipe. on this particular manifold the customer wanted stainless.

    i'm curious of everyone's experience with welding the inside of the flange to pipe joints like on the head flanges and collectors etc.

    i've always welded the inside of the joints and not had any problems. i've seen lots of other manifolds without any welding on the inside but don't know if there has been a problem as a result.

  • #2
    I think welding the inside makes for a cleaner part. I too have seen production headers without the inside welder but I usually go back and weld them up if I can and then grind them down (open them up). The aircraft exhaust shop I worked at several years ago always welded the insides (what ever that means I don't know).

    BTW - those are some very nice looking headers.

    DW Metalworks LLC
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    • #3
      IMO reasons for welding the ID

      Less distortion to the flange.

      Better flow

      Less chance of cracking at the flange to tube.


      • #4
        I've always welded on the inside as well.
        Very nice work!!!
        at home:
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        at work:
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        • #5
          stainless headers

          Nice welds there Wierracing......Did you back gas the tubes? If not, what rod did you use? It has been experience if no back gas is used there is plenty of "sugaring" on the weld's back side. I read somewhere once of a type of low heat stainless rod used to weld plumbing for a turbo setup.


          • #6
            hmmm, how much would you guys charge for a set of over the transome headers for my 454 jet boat


            • #7
              Very nice looking welds!

              I too weld the inside, just a habbit i gues.


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              • #8
                I weld both sides on SS or the black weld-el's. When it comes to Aluminum intake manifolds though I've always had bad luck with the tube burning back from the flange while trying to get a puddle on the flange.

                I'm not sure why, but even though i can get both done on AL it just stays looking a whole lot better if i do the outside only. On SS as long as the inner and outter beads are a little spaced apart from each other they weld easily, but if they weren't back gassed and you have any sugaring on the inside of teh part where your inner bead will be then you will have issius getting it to look good, not to mention boiling half the important elements from the SS while you're at it LOL (not sure if that's completely true, but you know what i mean i think... dull, gray, porouse welds on one side or the other if it wasn't back gassed)
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                • #9
                  The joint<s> need to add up to .109". Most people making manifolds do not make their flange joints full sized. They throw down whatever looks pretty doing two passes on a 1/16" rod, or one pass on a 3/32" rod. The welds do not flow to the size needed.

                  If the exterior joint is full sized there is no need for the join to be welded. If the exterior joint is undersized the inside will add to that.

                  Otherwise, I think it should be done:
                  • too say that you do it set yourself apart
                  • can't hurt the flow compaired to a flat joint into the stream inducing reversion (The best would be for the pipe to be the smallest hair larger ID than the flange's ports. That will reduce reversion back into the cylinder.)
                  • will add to the strength if the exterior weld is undersized for whatever reason