Repairing Cracked Exhaust Manifolds

Discussion in 'Original Drivetrain Topic' started by Mark80Z28, May 9, 2008.

  1. Mark80Z28

    Mark80Z28 Veteran Member

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    Aug 16, 2006
    Ohio
    When I had my motor rebuilt years ago, I had to find a set of exhaust manifolds due to the fact that both of mine were cracked. I kept the originals, and I was wondering- if I decided to, could I get mine fixed, would it last, and would it look right? How much would I probably be looking at to have it done?
     
  2. Gary S

    Gary S Administrator Lifetime Gold Member

    You can weld them, but if they broke once, they will likely just break again. Clean them up and hang them on the wall to look at. Used ones that haven't been broken yet are better for the car.
     
  3. Hotrodpaul

    Hotrodpaul Veteran Member

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    Nov 30, 2005
    Houston, TX
    Welding up Cast Iron is tricky because of the high Carbon (Graphite) content. Normally, the parts must be preheated to about 700 -900 deg F then welded with high Nickel content rod, then allowed to slow cool from the preheat temp to room temp. This will keep a phase called Martensite (very hard and brittle) from forming, causing cracking and other problems. It is an involved process and should be done by someone who has done them before. I also noticed that the earlier manifolds (69 and earlier) seem to have been cast from crappy material and 71 and later are better since I tried welding on both. You might get some scrap manifolds and practice on them.

    Paul
     
  4. Kurtz

    Kurtz Veteran Member Lifetime Gold Member

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    Dec 17, 2004
    Ontario, Canada
    Jerry MacNeish of camaro Hi-Performance will weld them for you - www.z28camaro.com. But, like Gary said I'd look for some good used ones at swap meets or on ebay.
     
  5. Mark80Z28

    Mark80Z28 Veteran Member

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    Aug 16, 2006
    Ohio
    I have a good set on the car now. They look like the originals, minus the holes for the smog tubes. I was just wondering if it would be practical to fix the original ones if I ever decided to. Doesn't sound like it would be.
     
  6. Bowties_1971_Z

    Bowties_1971_Z Veteran Member

    just have them brazed.
    ya you see the little gold "blob" of brass there but soon enough it will darken enough that most people won't notice it.
    thats the easy/cheapest way to do it. but it all works the same if your just looking for function and not show;)
    and as you can see from the post above its a heck of alot less complicated and im sure it will save you some big $$$$
    if the crack is in a place nobody will see just braze the sucker.
    if you can see it braze it anyway. dribble some oil/grease on it and it will darken with it burning anything on the manifolds.
     
    Last edited: May 12, 2008

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