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Thread: Exhaust Manifold Flange Stud

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    Darth Vader AUSMHLY's Avatar
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    Exhaust Manifold Flange Stud

    The six Exhaust Manifold studs at the exhaust flange seem to be the original and worn out. I've cleaned them with a brass wire brush to find out they're not really in good condition. I thought about using a die and seeing if that would help clean them up and hopefully get a better bite with the brass nuts. Would the die be a 5/16-24 UNF? If I did that and it didn't help, being the studs are so firmly in place, can I re-die of a different size? If so what size and where would I get those brass nuts?

    Because of how old, and worn they look, replacing them would be best; but my concern is how to get them out without snapping them in place. They've been in place for over 55 years and most likely they aren't going to come out without a fight. Pick your battles they say. What is the best procedure to remove them. Can it be done without removing the manifold?

    I only went into the supermarket for some milk and left with a cart full of food, aka, I just wanted to replace the exhaust flange gasket, and this may turn into another project. Oh the joy.
    Last edited by AUSMHLY; 11-13-2019 at 08:16 PM.
    1964 BJ8 phase II

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    Yoda
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    Re: Exhaust Manifold Flange Stud

    They can be removed in situ, using Vice Grips for example but, yeah, you'll likely snap one or two. I did this, and snapped one, but was able to MIG weld a nut on the stub and extract it. Probably the best way to extract them is to weld a nut onto each one and use a socket to back them out. IIRC, they are 5/16" UNF on the nut side. 'Re-dieing,' I think is a bad idea--what are you going to cut them to, 1/4in?--because they would become even weaker than they already are due to decades of heat cycling and exhaust gases. Get some penetrating oil--I like Kroil--on them repeatedly best you can, and work them out carefully (back-and-forth, more oil, back-and-forth, etc.). IIRC, the manifold end of the studs goes through, so get the penetrating oil on there if you can. If you use Vice Grips, try to turn them out straight, i.e. no twisting side-to-side as that seems to be what breaks them.

    FWIW, I tried SS studs from the late Doug Reid, and I felt they broke easier than the normal mild steel ones. I gave up on the brass nuts and have been using double-nutted steel nuts with high-temp anti-seize on the threads successfully.

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    Darth Vader AUSMHLY's Avatar
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    Re: Exhaust Manifold Flange Stud

    Quote Originally Posted by Bob_Spidell View Post
    They can be removed in situ, using Vice Grips for example but, yeah, you'll likely snap one or two. I did this, and snapped one, but was able to MIG weld a nut on the stub and extract it.
    Thanks Bob,
    Youtube showed how to do that. My concern...remove situ with Vice Grips, stud snaps clean at the flange so a nut can't be welded, or enough stud left to weld a nut then it re-snaps clean at the flange. Okay, remove the manifold. Is removing the broken bolt something I can do with a drill extractor or is it now a project for a machine shop?

    If I simply clean the threads with a die, and the brass nuts have a little play, can I install with a metal washer, metal split washer then the brass nut? Or washer, 2 brass nuts?
    1964 BJ8 phase II

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    Yoda
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    Re: Exhaust Manifold Flange Stud

    Even if the stub snaps level with the flange you can still weld a nut on; just fill the nut's ID with weld, and hope enough fuses with the remains of the stud. I've used various types of extractors with mixed results, getting a nut on the stud stub (heh) any way you can is the best bet IMO. You will have a hard time getting a bit in the center of the stud unless you have the manifold on a drill press.

    I mentioned what has worked well for me (I still have a half-dozen of the brass nuts in my parts dresser): double steel nutting on top of Grade 8 flat washers with high-temp anti-seize. Brass is malleable and eventually will give; I suspect brass nuts were used to prevent the studs and nuts getting fused by rust, before good anti-seize became available (I don't recall anti-seize being used way back when, but it could have been).

    Edit: If you do remove the manifold and get the studs out, I would flat-file the manifold flanges (you can do this with the studs in place, but not as completely).

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    Jedi Knight Bob Claffie's Avatar
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    Re: Exhaust Manifold Flange Stud

    Another caution on using a die. A die, even of the same size, will remove valuable material. If you decide to go this route use a "thread chaser" this tool will clean the existing threads without removing any of the original metal.
    Thank goodness the MG is finally gone, replaced by another Corvette

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    Yoda HealeyRick's Avatar
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    Re: Exhaust Manifold Flange Stud

    My advice is to remove the entire exhaust manifold and take it to your local machine shop. They'll know how to remove it They may have to do an EDM (google it} removal, but it beats fighting it on your own.
    Rick

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    Yoda
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    Re: Exhaust Manifold Flange Stud

    Quote Originally Posted by Bob Claffie View Post
    Another caution on using a die. A die, even of the same size, will remove valuable material. If you decide to go this route use a "thread chaser" this tool will clean the existing threads without removing any of the original metal.
    Corollary: Thread chasers do not work well as dies (unless you want your bolt to have Peyronie's Disease).

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    Jedi Warrior red57's Avatar
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    Re: Exhaust Manifold Flange Stud

    Another vote for HealeyRick's advice. If you haven't fought this kind of battle before, your stress levels will be much lower and the end result better by taking it to a qualified shop and having a pro remove these and install new ones for you - then reassembly is almost fun (and I prefer the use of Brass tall nuts, for the next time the gasket needs to be changed).

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    Obi Wan Patrick67BJ8's Avatar
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    Re: Exhaust Manifold Flange Stud

    When I overhauled my engine I had a few studs break off and I took them to a shop and with all their knowledge and equipment they really had to work the broken studs to get them out.

    i then took both exhaust manifolds to a powder-coating shop and had them ceramic coated for high temperatures. Flat black coating which seemed appropriate.

    For new studs I installed stainless steel studs with the long/tall brass nuts. The studs were made by the late Healey enthusiast Don Lenschow.
    Patrick
    '67 Metallic Golden Beige/Red
    Owned since '72

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    Re: Exhaust Manifold Flange Stud

    I also took mine to a machine shop to have them removed. I snapped two off while trying to remove them myself. good luck

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    Luke Skywalker
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    Re: Exhaust Manifold Flange Stud

    I am afraid that I took a different route with mine. I guess that I should have tried heat treatment first but I do not have a gas torch.

    So I cut them off flush marked the centre and proceeded to drill a small hole using my ordinary hand drill - I did not have a pillar drill at the time, I then enlarged it with a slightly bigger drill bit and again with a bigger size and caved the sides in with a hammer and centre punch to get the rest of the stud out. I also bored one out and re-tapped it, it ended up a little skew but I was still able to mate the holes, on the opposing flange, up with it.

    'There is rough - dog rough, and Bob Hughes'



    Bob

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    Re: Exhaust Manifold Flange Stud

    If you're going to do it yourself I would suggest you get a good quality stud extractor that grips the stud where it enters the head.

    https://shop.snapon.com/product/supplemental/200-Series-Stud-Remover-Installer-Sockets%2C-3%2F8%22-%2C-1%2F2%22-drive/AST20038

    Used with care they worked for me. You need to make sure the face of the socket is flush with the base of the casting and don't put any bending force on the wrench when you turn it.

    AJ

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    Jedi Trainee Joe Schlosser's Avatar
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    Re: Exhaust Manifold Flange Stud

    As AJ said, Stud extractor and a lot of penetrating oil, PB Blaster is good. They also make reverse drills for stud extraction
    Joe Schlosser
    SCCA National License, Retired
    60 Bugeye, since 1966
    SCCA FP, sold but not forgotten

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