Manifold stud removal

JasonNCJasonNC Expert Adviser
in HUDSON Posts: 720
i am trying to replace the studs on my Twin H manifold with longer bolts in order to put more gaskets on the base of the carbs.  I was able to remove the two studs for the rear carburetor by spraying them with PB Blaster and using two nuts tightened against each other.  I tried the same method on the front studs but only managed to strip the nuts on them. My buddy is a welder and he wants to weld a nut on each stud and then heat the manifold where the bolts go in with his welding torch.  I'm ok with welding the nut on the stud, but would prefer heating the stud as opposed to the manifold itself. Any advice will be greatly appreciated. 


  • bob wardbob ward Senior Contributor
    Posts: 942
    Yes, weld nuts onto the studs and after that quickly heat the studs until they get red hot then take the heat away and let them cool. Studs will unscrew with almost zero effort.
    Lockyer Valley, Queensland
  • FrankvintagefullflowcomFrankvintagefullflowcom Senior Contributor
    Posts: 929

    Although Bob's probably right on, if it does continue to resist, some penetrant and shock should do it. Spray, tap tap tap with a light hammer directly on the stud, rinse, repeat. If it begins to turn but with too much effort, go back in, spray-tap tap tap. wiggle it with each attempt. Patience.....remember: no matter how long it takes to un-screw it, it's far less time/aggravation than you'll invest to fix a broken-off stud. 


  • Jon BJon B Administrator
    edited March 17 Posts: 6,431
    Just to further elaborate: Before heating, the stud is pretty much "welded" by accumulated years of rust, to the manifold. 

    Heating metal causes it to expand, cooling it causes it to contract.   If the stud first expands than contracts (and then maybe does this again), each cycle of expansion / contraction causes it to open up a space between it and the threaded manifold.  Penetrating oil can then get into this gap and help lubricate the threads.

    Anyway, that's the thinking!

    The gentle tap-tap-tapping sets up a vibration that helps conduct the penetrating oil down into that opened-up gap between the threads of the stud, and those of the manifold. 

    It's my contention that -- when pulling a brake drum with a puller -- one should tighten the puller and then tap with a hammer around the perimeter of the drum to set up a vibration that gradually causes space to open up between the axle and the drum.  This concept works best, of course, when there is some tension on the puller.

  • duncanduncan Expert Adviser
    Posts: 743
    my friend give me a secret on how to remove seized studs head stud till red and apply a wax candle around stud so wax penetrates threads screwed into manifold and wait till cool and easily remove stud. I was very surprised at how great it worked. Ray
  • JasonNCJasonNC Expert Adviser
    Posts: 720
    We got them out by welding a nut on both studs.  We heated the first sud and it broke off at the manifold with only a few threads showing.  After that we went to the 2nd stud and heated the manifold and twisted the stud while the manifold was still hot. We ended up having to weld on a second nut when that stud broke in half, but on this try it came out without much trouble.  We went back to the first stud and welded a larger nut onto the few threads that extended from the manifold and again heated the manifold.  It came out without a hitch.  My buddy welded the nuts to the studs from the inner diameter which was pretty remarkable considering what little metal he had to work with on the 1st stud that broke.  
  • 50ClubCoupe50ClubCoupe Member
    Posts: 172
    I got pretty proficient at welding the nuts on broken studs after I snapped 5 head bolts on a Model A.  After some experience I found it best to first weld a washer over the fractured stud and fill in with a nice weld pool.  Then I welded the nut to the washer, tacking the outside of the nut to the washer first and then filling the inner diameter of the nut with weld.  Initially I was having issues with spatter/incomplete welds when attempting to weld the nut directly onto the stud due to debris and rust (even after wire brushing) and the addition of the washer allowed for better welds.  Plus, by welding the washer first, then welding a nut, it allowed the stud to go through a couple of heating/cooling cycles so it helped break the bond with the block.  Since I've learned the trick I no longer fear breaking (most) studs and I'll never attempt to drill out a fractured stud again.
    1950 Commodore Club Coupe ('51 wide block 262 w/Twin H, 3spd non-OD)
    Mooresville, NC

  • 53hud5453hud54 Member
    Posts: 134
    For future reference for those of you working on rusty parts,there is a product called Kroil made by Kano Labs that is the best product I have ever used.A friend introduce me to this 40 years ago when he worked in a foundry that bought it in 55 gallon drums.PB Blaster used to be good but formula was changed a few years back and has more water in it.Give it a try,you'll be supprised.
  • RichardDRichardD Member
    edited March 18 Posts: 470

    Acetone & ATF 50/50--not DexIII.

  • befishers1befishers1 Expert Adviser
    Posts: 37
    I have also found using evaporust for a while works well.  As the rust is chemically converted the "weld" to the manifold breaks down and the stud comes right out.  I have done this by sealing a small cup with a hole cut in the bottom to the manifold then filling the cup and coming back a day later.  The first time I tried this it was a small part that I submerged overnight the stud came out with just my fingers.
  • Jon BJon B Administrator
    edited March 18 Posts: 6,431
    Wasn't aware of this product until now. 
    Not to be argumentative, but is this simply one of several brands that have the same ingredients?  Or is it truly unique?

    The concept of building a little "dam" around the rusty stud is interesting.  I guess you could simply purchase a tube (plastic? metal?) that's larger than the stud, fit it around the stud, and then "seal" to bottom of the tube to the surface of the manifold, but what would be the sealing material?  Sounds like a good concept (rather than just spraying CRC on it, and then hoping it will eventually work its way down into the threads.

    I'd think this would be  first step: build the little "dam" and fill it with penetrating oil / Evap o Rust, and then let it sit for a day, simply tapping the stud from time to time to set up vibration and help the oil work its way down.  Then, if THAT doesn't work, try the "torch effect" and simply heat and cool the stud a couple of times.  THEN try penetrating oil (or wax, as someone suggested).  Then if THAT fails to work, try welding the nut.

    In other words, start with the easy stuff first, and then go for a more and more complicated solution.
  • befishers1befishers1 Expert Adviser
    Posts: 37
    The same product as numerous others, it's just the one on the shelf at northern tool in town so the easiest for me to get.  The best material for temporary sealing is vacuum putty, this isn't​ the easiest material to find, used in composites work,

    It is an uncured rubber tape about an 1/8" thick, if you have never used it, it has a million uses, doesn't work for pressure works to seal a vacuum, under pressure it blows up like a balloon.

  • bob wardbob ward Senior Contributor
    Posts: 942
    The chemistry behind why heating can be useful.

    Rust as we usually see it is analogous to hardened plaster of paris. Most know that if you get solid plaster of paris hot enough to drive off the water content it turns back to a powder.

    Similarly the typical solid rust that we see binding a nut onto a bolt or a stud into a component has water bound in with the iron oxides. If you get the nut or stud hot enough to drive off the bound water (pretty much red hot) the rust turns from a solid to a powder of smaller volume and loses its grip.
    Lockyer Valley, Queensland
  • Jon BJon B Administrator
    Posts: 6,431
    Bob, from what you say it wouldn't matter whether one carefully heated the stud or bolt only, or the area of the block around the impacted stud or bolt -- the main thing is to break down the rust that occurs withing the threads of both.
  • bob wardbob ward Senior Contributor
    edited March 19 Posts: 942
    That's right Jon, in a sense it doesn't matter whether you heat the stud or the bolt or the part, the aim is to get heat into the rust to turn it to a powder, but then you get into the practical considerations of how to efficiently and safely apply the heat, not forgetting that we are talking red hot or close to red hot to make the magic happen.

    Each situation is different, but in the Twin H scenario under consideration I'd just be heating the studs and keeping the oxy off the casting as much as possible.
    Lockyer Valley, Queensland
  • Geoff C., N.Z.Geoff C., N.Z. Senior Contributor
    Posts: 3,286
    I have NEVER found a penetrant that can get in to a rusted in stud.  I have tried them all, including the 50/50 ATF/acetone mix.  
    If you're stuck in a hole, stop digging.
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