Stuck Ex. Manifold (oem upper to lower) stud

[aklackner]

Working with a rusted Oem cast Ex. manifold and rounded one of the 3 nuts joining upper and lower pieces. Other nuts were frozen to the studs but the studs spun out so are clear.

Center front is the problem stud/nut. Was dumb and rounded first with 12 pt long handled wrench then finished the job with a 5pt on impact wrench so the nut is like a marble now.

Manifold has been soaked with pb blaster both before and after rounding the nut.

Figure options are to take a cut off wheel to: reshape flats to nut, Remove with whatever will grip.
Reshape flats to the stud, Remove with whatever will grip (heat manifold with torch help loosen?)
Cut off stud/nut, separate manifold, have stud drilled out and thread repair (time-sert)

Any other (better) options I’m missing?

[coolhandluke]

PB Blaster is a solid first step. I've drilled out exhaust studs prior and it went surprisingly smooth.

[aklackner]

The plan is ultimately to have it abrasive blasted and extrude honed before something like zycoat.

I hoped to disassemble before I took it to a shop but they'll likely be better equipped to drill the stud out than I would be so I may just let them handle before I screw something up worse.

[Stin1]

This stuff makes pb blaster look like a bitch.

https://ads.midwayusa.com/product/12078 ... gIMp_D_BwE

[3pedalJohn]

Working with a rusted Oem cast Ex. manifold and rounded one of the 3 nuts joining upper and lower pieces. Other nuts were frozen to the studs but the studs spun out so are clear.

Center front is the problem stud/nut. Was dumb and rounded first with 12 pt long handled wrench then finished the job with a 5pt on impact wrench so the nut is like a marble now.

Manifold has been soaked with pb blaster both before and after rounding the nut.

Figure options are to take a cut off wheel to: reshape flats to nut, Remove with whatever will grip.
Reshape flats to the stud, Remove with whatever will grip (heat manifold with torch help loosen?)
Cut off stud/nut, separate manifold, have stud drilled out and thread repair (time-sort)

Any other (better) options I’m missing?

My recommendation is to get the engine up to temp if it's in running shape, turn off and then hit all the bolts and studs on the exhaust. Another method I have tried with some success on the small bolts for ABS lines is to tighten slightly then back them out, some time it works other times it doesn't.

If you can't run the engine, heat up the cylinder head around the bolt with small torch and try and remove.

You could cut off the nut along the axis of the stud to leave as much of the stud as possible, then remove the manifold form the head and you might have better luck at getting the stud out since you will have more room to grip. More material remaining on the stud the more options you have to remove.

[aklackner]

Heat is definitely an option but at this point the nut is totally rounded so I either need to try to cut it smaller to get a smaller socket on it, put some flats to get a wrench directly on the stud, or some other way to get a better grip on it/the stud.

Just to clarify this isn’t the studs on the head thankfully. Its a loose used OEM 96 spec JDM manifold that I’m just trying to separate (upper and lower halves) for.

Ultimately, I want to see if I can get it opened up and polished a bit (internally) and see what my JRSC thinks of it.

Hoping the short primaries and improved flow from honing/polish agree with the motor. NA I did well with the JDM 98 spec header but that’s never going to clear CA emissions. With the 96 manifold visual inspection shouldn’t be any problem and I still have the same 2.5” collector as the 98 spec. ID for the outlet on both is actually only about 55mm (~2 1/4”) due to a sort of double wall design at the collector that I can only guess is for anti-reversion purposes.

It’s not going to perform like a high flow header and is heavy but with the Koyo radiator and OEM fan shroud I don’t want to be swapping a header in and out to pass emissions.

Any way first step is to separate it so I can see what I can do with some ball hone brushes.

[RTW DC2R]

Any way to weld a socket or wrench onto the nub and see if that works?

[aklackner]

Any way to weld a socket or wrench onto the nub and see if that works?

I like this idea Now I want to try another nut welded to the stud/stuck nut so I don’t sacrifice a socket.

[shuttlepilot]

If you have access to one, a induction heating tool (mini ductor, bolt buster) would make quick work of exhaust nuts. A mapp torch would probably work too, but you need to be very careful with your aim. You must heat the nut cherry red to have a good chance to burn enough rust away to loosen the nut. The weld a socket/nut with a welder trick would work very well too, but if you don't have a welder, it is not likely worth the effort.

Penetrating fluid is mostly useless until you get the nut moving. Use it after you get fasteners moving to prevent them from binding further on new rust or galling during removal.

In lieu of a induction heater, I would high recommend grinding/cutoff tool one side of the nut away with fiber discs and a dremel tool. A 90 degree attachment would help with holding stability. If carefully done, you can reduce 1/3 of the nut into just the threads on the stud and severely weaken the remaining stripped nut. At that point you can take some vice grips to loosen and remove remaining bits of the damaged nut.

Once the nut is off, clean all the studs with a thread restorer kit like this to take care of any rust on threads:
https://www.amazon.com/gp/product/B000X ... 0DER&psc=1

Apply antisieze (nickel is my fave) very generously on the stud when reinstalling, but don't get it on the interior of the exhaust for fear of ruining the O2 sensor. Use only new nuts, the old ones are worthless since they likely had their size reduced by rust flaking from heat cycles.

[aklackner]

More great advise! Not quite sure what a bolt buster is but I want one. Torches I have but I worry about warping or otherwise damaging the casting with overly targeted/direct heat.

At this point I’d prefer getting the whole stud out and then chase the threads in the upper manifold to clean those up. Fortunately I do have a small dc Mig (century 90) so will be checking what sacrificial hardware I handy this weekend.

Agree on anti seize great when just enough but quickly becomes too much of a good thing.