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Brazing Cast Manifold?

Discussion in '40- & 55-Series Tech' started by roverpilot, Aug 13, 2005.

  1. roverpilot

    roverpilot

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    First time poster!! Anyway, anybody know anything about brazing(sp?) cast iron?? Old-timer here locally tells me that small cracks in cast iron (read "manneefold") can be repaired by brazing them, that welding may not be necessary...? Trying to salvage a 78 CA FJ40 exhaust manifold (made of unobtainium) to keep 'er stock.

    Thanks,
    Rob
    roverpilot@aol.com
    Gig Harbor, WA
     
  2. IDave

    IDave

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    No expert, but from what I've read, a good idea.
     
  3. roverpilot

    roverpilot

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    Let you know how it goes...n/m

    n/m
     
  4. brian

    brian SILVER Star

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    make sure you tie it down, before you put the heat to it.
     
  5. spotcruiser

    spotcruiser Geezer SILVER Star

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    Mine was cracked in about 6 places. Tossed it in the recycle bin and installed a Federal manifold and head pipe. Works great. Better than original.
     
  6. HawkDriver

    HawkDriver

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    Never heard of it, just heard that you have to heat it for like 5 days before and after you weld one. Don't know about brazing.
     
  7. Pin_Head

    Pin_Head

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    I brazed up a 6 inch crack in my '76 CA "nuclear reactor" manifold about 8 years ago and it is still fine. It is a common repair in cast iron.
     
  8. Doug_S

    Doug_S

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    If you have access to a stick welder you may want to check out www.muggyweld.com. They offer a kit that allows the use of a welded joint rather than one that is brazed. If you don't follow the muggy weld path then really the only way to do it is to nickel weld it which is very difficult and no guarantee of long term sucess.
     
  9. vtcruiser60

    vtcruiser60 SILVER Star

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    Yep you can braze cast iron. Cast iron welded correctly requires preheating (torch) and slow cooling (heat sinks or a leather glove over the weld). You can also tap the welds with a chipping hammer to strengthen the weld and relieve potential cracking. Cast is a pisser to weld and you need to be experienced from what I have seen. It requires grinding the crack out a bit, drilling out stress relieveing holes at the ends of the crack (do this before grinding) as well as layering your welds.

    Brazing works because it is basically a high temp solder. You are not welding, but soldering the crack. Brazes can work on manifolds because the manifolds get hot, but not hot enough to melt the braze. Again, brazing does not fuse with the cast....it lays a bead of metal over the crack.Cast iron can rust, especially beneath the braze weakening the set up.

    If you have nothing to lose but time, try the braze or have a shop do it for you. You'll be out the 30 minutes of labor and some gaskets. But, if you want them to do it right, have them weld it. If done by an experienced welder, it won't fail again.

    Oh....probably good to have the manifold decked after welding or brazing. The heat might warp it a bit and cause new exhaust leaks after installation. If it is warped a bit (a straight edge will tell you this), you'll want a machine shop to hone it a bit and make it flat again.

    Incidentally....I just went through this with my 96 Tacoma....ended up buying the part new rather than welding. It was a $150. I couldn't find the sticks cheap enough and decking the manifold was going to be another $50 bucks. It was an easy justification for a new manifold.

    Hope this helps. Let us know what you do.
     
  10. HawkDriver

    HawkDriver

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    If I were going to the trouble I'd just buy a different one and forget about it. Wouldn't want it failing again down the road. Ebay has them from time to time. Someone might have one in the classifieds.

    Very informative thread, thanks for posting.
     
  11. ar2stp48

    ar2stp48

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    Compared to welding with a nickel rod, brass is much better. But they also make a cast iron rod that works great. Do have to pre heat but not as much as most want to indicate. Cooling is simple: put in in a tub of dry sand and cover til cooled.
    Your 78 have the 3 piece exhaust manifold? Have the one off my 78 in the barn; make a small offer and pay the post; I have no use for it.
     
  12. Landpimp

    Landpimp GOLD Star

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    I would guess the best local guy to weld a manifold is Bill at UP Rad and Muffler.

    John