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Thread: exhaust manifolds on 94 gmc 2500 350 engine

  1. #1
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    exhaust manifolds on 94 gmc 2500 350 engine

    my recently acquired truck went in for safety inpsection and emissions test; would not pass either for various reasons but a common element as an exhaust leak whicj i traces back to the exhaust manifold on the right side cylinder bank

    it appears that the manifold may have been off for some reason before i got the truck and who ever put it back on did not boyther with any exhaust manifold gasket

    we shall fix that

    we has to cut off off the heads of all the fasteners due to corroision and we are fixing that

    we had to cut all the fasteners at the manifold/y-pipe again due to corriosion

    now for the question

    i notice, on both banks of cylinders, a mixture of bolts/cap screws and studs/nuts sucures the exhaust manifolds to the heads

    did GM use both on the same engine or did the previous owner use what ever he had laying aroundf when putting things back together

    lastly, does it matter if i use bolts or studs/nuts

    the chap at the UAP/NAPA store tells me it does not matter which I use

  2. #2
    Senior Moderator chevychase's Avatar
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    Will be both ..can use either ..but a few studs helps hold manifold on till you can start other bolts..if that makes sense.

    Gitter done have fun. Running on empty...running blind...running behind.....

  3. #3
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    If they have been on there a long time the manifolds will warp and not all the bolts will line up, I ran into this problem when I replaced my motor, to help getting the manifolds back on, I had to use all thread leave some sticking out, that will flex screw it in tight then slide the manifold on might take some arm to get it then you can get the bolts in and not get them cross threaded, been running like this since 05 never had a issue or leak that I know of.
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    finished getting the exhaust manifolds off today: i have done some rotten jobs in my time but this has to rate up at the top of the list.

    adter I got the manifolds off, all of the stud/bolts came outof the heads relatively easily except for one; one of the hardest to get at of course; at the back of the right hand side head; the a/c dryer blocks easy access

    there is about 1inch of the bolt sticking out of the head and so I can get hold of it.

    this is my first go around on GMvehicles and the 350 V8 engine and so perhaps someone can give me some advice on how to get this fastener out

  5. #5
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    They make a stud removal tool that should grab it, check at your local parts store as some of them lend out tools. Some heat applied from a torch on the inside of the exhaust port towards the stud may help as well.

  6. #6
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    we are new to working on GM vehicles

    had to get a new right side exhaust manifold; the flange at the y-pipe connector was damaged; looks like it had been broken and the previous owner had welded it up' the material was so thin that when I tried to remove the attaching hardware, the flange fell apart

    so - a new manifold is on my work table as I type this

    now for the dumb question; the manifold/head gasket has two sides (duh); one is shiny & ,ettalic and the other is what appears to be a fibre surface - which side goes against the head

  7. #7
    Senior Moderator chevychase's Avatar
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    Slick toward engine/fiber surface manifold. When you install manifold tighten middle bolts first..the work your way to front ,and back .
    Middle bolt snug..not torqued..then a bolt to the left of it..then a bolt to right of middle bolt..snug..then when you get all in torque to specs in same sequence. 11ftlbs first pass torque to 22 2nd pass
    Last edited by chevychase; 10-26-2012 at 05:40 PM.

    Gitter done have fun. Running on empty...running blind...running behind.....

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    Re: exhaust manifolds on 94 gmc 2500 350 engine

    I think the book says to give it another 55 degree turn for center bolts on head and 65 degree turn on the 2 outer bolts. Just thinking from the top of my head from when I read it...

  9. #9
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    usually it says on the gasket
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  10. #10
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    Quote Originally Posted by chevychase View Post
    Slick toward engine/fiber surface manifold. When you install manifold tighten middle bolts first..the work your way to front ,and back .
    Middle bolt snug..not torqued..then a bolt to the left of it..then a bolt to right of middle bolt..snug..then when you get all in torque to specs in same sequence. 11ftlbs first pass torque to 22 2nd pass
    Hate to differ, but all instructions sent with manifold gaskets I've seen said the shinny side towards manifold. Not that it probably makes that much difference.

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