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My Exhaust Manifold Leak V2

Discussion in 'Intermediate CJ-5/6/7/8' started by dane71, Oct 18, 2020.

  1. Oct 18, 2020
    dane71

    dane71 Member 2019 Sponsor

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    The first thread was mostly me complaining and wondering if I missed the obvious. Anyways...

    I took it apart again today and I think I found the main problem. On cylinder 1 (front of the engine/vehicle) the exhaust gasket doesn't seem to come up high enough on the bottom edge, so the exhaust gas finds its way out of the manifold at the bottom corner. Has anyone ever seen this issue? I'm guessing for a solution I should find someone that is able to weld on cast iron, so they can make the flat surface of the manifold extend out and then I'll get it milled flat again. Or is brazing a good solution-I know nothing about it. I'm open to ideas!

    forum1.jpg
    In the picture below you can see the leak at the bottom right of the port, and the light gray outline of where the manifold sits against the gasket.
    forum2.jpg
     
    Last edited: Oct 18, 2020
  2. Oct 19, 2020
    PeteL

    PeteL Member 2020 Sponsor 2019 Sponsor

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    I would check the machined face of the manifold for flatness. Maybe it can be re-surfaced if it is warped.

    But also, it looks as if the gasket is kinked at that point. Why is that...?
     
  3. Oct 19, 2020
    dane71

    dane71 Member 2019 Sponsor

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    I thought a warp was causing the issue so I had it machined and tried a new gasket, and now its leaking out the same exact spot again after only a couple hours of driving. Been very careful to follow the service manuals torque procedure both times as well and retorqued several times along the way

    Im not sure on the kink. I checked it and everything is flat on the sealing surfaces. It mightve been when i pulled the manifolds off, it felt like they were stuck to the gasket.
     
  4. Oct 19, 2020
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    I'd say it's clearly core shift. Is this an original or repop manifold? Unfortunately the left manifold is less plentiful because it changed in 1980 for the 360.

    This isn't the only supplier: https://www.bjsoffroad.com/Exhaust-Manifold-Driver-Side-1971-1979_p_733.html

    Oh, sorry - it's a 258. Assuming it's a 1V, you really want to keep the YF?

    1975 JEEP CJ5 4.2L 258cid L6 Exhaust Manifold | RockAuto

    The manifolds from an '81 or newer 258 will work with some minor mods. I am running manifolds from an '85 CJ on my J10. These are much smoother, much lighter, and get rid of the gasket between the manifolds. The intake is a 2V manifold though.
     
    Last edited: Oct 19, 2020
  5. Oct 19, 2020
    Fireball

    Fireball Well-Known Member 2020 Sponsor 2019 Sponsor

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    You might look at different brands of gaskets too. They may have a smaller port size that would solve the problem.
     
  6. Oct 19, 2020
    dane71

    dane71 Member 2019 Sponsor

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    Interesting, I'm gonna read up on that. "China" is cast into it so I'm guessing it's not original. I'm liking the YF so far but still don't have much time behind the wheel on this Jeep, I heard the 2 barrel is only like 10 horsepower more isn't it?
     
  7. Oct 19, 2020
    dane71

    dane71 Member 2019 Sponsor

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    Yeah I'm definitely gonna see what else I can find. The holes in these gaskets (Fel-Pro MS9982) are so big compared to the actual ports. Extra tolerance is nice but I'd rather have to trim something than have this happen!
     
    Last edited: Oct 19, 2020
  8. Oct 19, 2020
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    Heck - I've been looking at the carbon and thinking that was the shadow of the port. You realize that this manifold is supposed to bolt up to the cylinder head with no gasket? That would likely solve your problem. Possible there is a gasket available that fits the smaller port size, but you should not need it. What year is this Jeep and engine?
     
    Last edited: Oct 19, 2020
  9. Oct 19, 2020
    dane71

    dane71 Member 2019 Sponsor

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    This is a '74 with the 258. I think a bit of the carbon shadow is simply because there's a void there where the gasket isn't covering, but I could be wrong. And yeah I know the factory didn't use the exhaust gasket, it just came with the intake one to use in case of less than perfect manifolds. Maybe I should ditch it then and only use the intake gasket? That's something for me to consider... Good idea! If I do that I might use a thin coating of Permatex 81878 copper max temp RTV, just to be safe. I would have the manifold checked for flatness first of course.
     
  10. Oct 19, 2020
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    I would try it without the goop first. That seems like something that would blow out pretty soon. You can check the flatness yourself if you have a good machinist's rule that is long enough and feeler gauges. Others with more machining experience might have other ideas. Apparently machine shops have a long bar of some type that they use to measure surface flatness.
     
  11. Oct 19, 2020
    PeteL

    PeteL Member 2020 Sponsor 2019 Sponsor

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    I thought exactly the same thing at first.

    If the manifold was already machined, maybe the mating surface on the head needs to be checked for true.
     
  12. Oct 24, 2020
    dane71

    dane71 Member 2019 Sponsor

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    A guy at my work directed me to a local expert he knows, who runs an exhaust shop, and I talked with him today. He said he could weld the manifold so I can have it milled for a larger mating surface, but he said the main thing is that the type/material of gasket im using sucks, and that i should try using some type of sealant as well. I'll update when thats taken care of, but its getting cold quick so things could take time.
     
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  13. Oct 31, 2020
    dane71

    dane71 Member 2019 Sponsor

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    I got to drive around tonight after installing the remflex gasket. I think that took care of my problems! The port does come up a little higher than the gasket I was previously using, like I hoped. It seems like a good product. I did not use any sealant/etc with it. I will update if it gives me issues.
    Happy Halloween!
     
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  14. Nov 1, 2020
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    Remflex gets good reviews from header owners. Glad it worked for you. (y)
     
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