Hi Everyone,

I've decided to replace my, slightly leaking on one cylinder, exhaust gasket. This has been ongoing for awhile and I've tolerated it because I don't want to break the studs on removal, and make a tiny annoyance into an all day project.

I've been spraying the nuts daily for a couple months with PB Blaster, but upon heating them with a torch and trying to loosen, they are still tight, zero movement, feel like they will break. I have replacement studs and nuts for all of them, and easy outs, drills, taps, if things go wrong.

Any ideas of how to proceed without things going wrong?

Thanks, Jim

Torch = oxy/acet - correct?

I always do this, nothing else. I heat until red and then break with a 3/8" drive 6-point socket on a small breaker bar.

I've had poor success with propane and/or penetrants.

Kitty-Grey's suggestion of wire-brushing is nice lagniappe. I sometimes do this with a dremel if the threads are look bad.

Then I clean threads on stud and nuts with tap and die.

I use the same method on older vehicles eg. I just removed the manifolds from a 1947 truck that had been in a open shed for 50+ years.
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240 drivers / parts cars - JH, Ohio

Hi,

My best advice is to do just exactly what has been posted here, of which, you have done.
I agree with the choice of using heat for the nuts.
The studs can be heated but I would hold a rag on the stud for a seconds, to help it shrink as fast as that aluminum head is going to suck heat away!
Hopefully, you won’t need use it when you get that far in!

I can give you a little background on what you are dealing with.

When Removing the nuts, you are dealing with steel on steel and a fine crack between the two parts.
You can try squeezing the nut a little with Vice Grips to mash them a little out of round, but do not screw up the flats.
There are cracks that runs up and down in a 60 degree angled form.
Think of two opposing “V’s,” side by side, parallel to the axis of the studs. Squeezing shift those angles to possibly slide. We are talking pressure only at the molecular level.

The threads in a hex nut are holding the manifold in place, with its flat face shoulder, but the stud is still stretched!
Each thread on both ends is pressured to one side of their respective thread angles, thus making a metal to metal contact.
The aluminum threads are trying to hold onto the stud just as equally as the nut.

We need to work with those two forces to rattle open that fine crack in
both parts, since they have the same thread clearances we can move in!

On those mating parts there is a space at the top and bottom of the bodies of threads.
It was made this way by truncating the tops off creating root clearances.
It’s a space made to allow for debris, lubricants and most of all inconsistencies in dimensions due to material stress and distortion.
There are many more reasons for root clearances.
The main One is this!
The principal of threading is helical and is a theoretical 100% “V.”
That idea of thread fitting inside another thread cannot be made to work, especially on the internal side!
This is why a calculated maximum strength of a threaded hole is rated at 75% and the reason for a “tap drill size” chart. It does the most truncating.
This is because, It takes four times the torque, on the tool, to gain that extra 25%! Not practical nor needed!
The Rule of thumb is, at 75% the depth of thread a tapped hole needs not to be any longer, than one and one-half the times the diameter of the bolt or stud used to get its maximum strength.
This means, the stud or bolt will snap off before the threads in the hole will strip out!
I have never seen a tapped hole with stripped threads but a bolt thread in them, yes! All due to some sort of assembly error!

In actuality, you are working with the nuts first because you can apply axial torque to them.
But you can apply some lateral force to the stud by tapping in line with the axis or the center of both threads.
You want to shake any play in between those two fault lines a little bit.
You want to shift particles out of their “homely little pockets of togetherness” into those root spaces. That Vice-Grip squeezing stuff comes in about here. Just a little pressure is all to move in the tiny spaces.
You can do it hot or cold or in combinations while tapping them with a small hammer.

Ok now!
What it’s going to come down to, you are going to “vibrate” both the nut and the stud, working, within the two threads tensions, by striking against the stud and jolting the tensions. Just decent thumps at any speed you like.
This temporarily shifts the cracks and the crusty little varmints start falling out into the root cavity!
I suggest you add on an extra nut to the end of the stud, if you have any extra threads, to have something to beat on.
By having them double nutted, you can use either one to rotate the stud nut or the stud.

You want to work carefully at twisting the assembly “back and forth” with lots and lots of patience with “time” on your side.
It is the key to success!
Turning them consistently, each way, yes, I mean tightening too! Loosening with the same pressure that doesn’t snap anything.
Yes, tapping on them with the hammer eases up on the hands and tends to break up the monotony! Moving to another stud, helps!
All the while, spraying and letting the oils soak in.
These flakes and crystals need to shift around. They need to crunch a little, to slip a little.
A little space leads to a working that space of a little part of turn. After a bit of this several times, I then go back to pushing it a little more on the others, a few times!

Spark plugs use the same loosening and tightening procedures.
Oil and only the thoughts of any cussing words, will help keep your cool!

Phil

Phil,

Once again you've gone above and beyond. Your Machine Man name fits, and I enjoy your machine theory, philosophy, and practice very much.

I had though about just slicing across the nuts (without touching the studs) with a dremel to release them. This will probably be mine last chance effort.

For now I suppose I'll spray and heat, and wrench, and repeat.

Thanks, Jim

If not already, use a steel wire wheel on a drill or a steel wire brush to remove rust formed on the exposed stud thread.

Use a coarse and then at the interface of the nut where the stud thread erupts, a fine wire wheel to gain some relief at the mound of corrosion of the rust where the nut inside diameter begins at a usually slightly chamfered edge on the inside diameter of the nut. Wear eye protection. Maybe breathing protection for the rust that become air borne powder.

Doing so may help penetrant oil to enter the thread interface between the retaining nut and the stud.

Also, as Haynes says it in UK commonwealth English, firmly, yet gently tap around the top of nut using not a small hammer, maybe a heavy screw driver handle, and pointed punch to at least cause vibration to foment fracture to the corrosion bond between the nut and stud. The vibration may work into the carbon-steel stud to light aluminum alloy cylinder head.

You can also use penetrant like the Liquid Wrench, Kroil (see gunsmiths that sell it), and PB B'laster (you are already using) Penetrant. I'm unsure which penentrant oil is best for weakening or dissolving iron alloy rust corrosion on factener hardware any more.

In articles here on your brickboard, there exist some notion of a 50/50 mix of ATF (probably Dexron, Mercon, and the like, not "Type F or G") and acetone to loosen fastener hardware yet the effect does not survive heat and does not attack corrosion.

Hope that helps.
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kittysgreyvolvo,

Thanks for the great ideas. I'm making progress, no hurry as I'd rather not break any studs.

Jim

Hi,

I have torches available, but I've taken off several gnarly exhaust manifolds using a variation of Kitty's hammering technique. I try to avoid using heat unless absolutely necessary because if the studs are grade 5 or higher, they are heat treated and will lose some strength.

I don't advise using a center punch, but instead use a small, sharp, cold chisel. For this type of work I usually grind or forge the tip of the chisel to about 30 degrees from the normal 60 degrees, then harden and temper, but you should be able to work with a stock chisel. A thinner chisel cuts faster, is all. Wear safety glasses.

Cut into the nut at 2 opposing points on the face of it. This means the chisel will be moving parallel to the stud, toward the head. DO NOT cut into the side of the nuts, as this will bend the stud. If you can't access opposing points, cut at any points you can reach. The cutting will cause the nut to expand, the oil to penetrate, and eventually loosen either the nut or the stud from the head.

This works every time, unless you run out of patience. I've never damaged, or had to replace a stud with this technique, but I do use all new copper nuts. This also works well on thermostat housings with their delicate studs.

Good luck,
Peter

maplebones,

Thanks for the great ideas. Like yours and kittsvolvo idea, I hadn't thought of working them this way. I usually just dremel cut them off if need be, but that takes awhile.

Jim

Build wrote--"I've been spraying the nuts daily for a couple months with PB Blaster, but upon heating them with a torch and trying to loosen, they are still tight, zero movement, feel like they will break." By torch do you mean oxy-acetyline? If not, you're wasting your time. If you only have a propane torch drive the car to a shop that has Oxy-ace and ask to have the nuts heated cherry red (one at time of course) and then quickly break them loose. The idea is to expand the nut but do so fast so the stud doesn't get heated as well. == Dave

Dave,

Yes oxy/acetyl. I'll try a few more times, but feel they haven't budged a ten-thousandth. I've loosened many before, but none this small diameter. I've also had success heating the nut, then hitting the stud with liquid nitrogen, but there isn't enough room to do it here.

Thanks, Jim

I sprayed mine also with PBlaster cold. Then just drove the car normally. When I parked sprayed them again while they were hot. I did this daily for a week.
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Did you have success? I've sprayed them cold daily for two months and they still seem stuck.

Yes. But I also sprayed mine hot right when I parked.
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I've also sprayed mine hot many times over two months, but cold daily before driving.