XK120 Inlet Manifold Removal Quandary

I’m in an exceedingly tough spot here. I have several days’ worth of time trying to remove my inlet manifold and, it’s just not happening. I’m speculating that this car may have spent no small amount of time parked down at a local marina in days gone by. Or at the least, a gasket that weeped moisture. How else to explain fully half of the studs being well and truly bonded along the lengths of their shanks by rust and corrosion? Here’s my succession of removal attempts:

  1. Saturated all studs with PB Blaster for a few days. Then I double nutted the studs and was able to remove almost half of the 18 studs.

  2. Where double nutting wasn’t good enough, I then welded the nuts to the studs. That worked for one or two. The others just sheared off.

  3. I profiled the remaining studs flush with their bosses. Then I center punched all studs and drilled all 5/16" studs out to 1/4" inside diameter to within 1/2" of the manifold/ cylinder head joint. My thinking was as this leaves so little substantive “meat” left in the shanks, surely with some more penetrating oil and chisels (!!!) used as wedges (not at the joint face though) it would have to pop off by now. Nope. Not even the barest hint of a gap starting.

What to do, what to do as my options are greatly winding down.

Some background:

I just wanted to remove this along with the carbs, water pump, generator, flywheel, etc. so as to leave a basic long block I can then take to a rebuilders prior to a thorough internal going over. It last ran in '82. If I take it over in its as-is condition now I’m going to feel a sense of shame as I, too, have a machinist’s background.

So now I’m researching chemical options:

I’ve seen on the 'net that alum (potassium aluminum sulfate) as sold in some grocery stores for home pickling along with water is supposed to actually eat the studs but leave the surrounding aluminum intact. Other posters all say that the solution must be kept heated to almost boiling otherwise the solution will want to re-crystalize.

Muriatic acid? Seems too corrosive and how do you dilute it down while still maintaining its effectiveness?

Sulfuric (battery) acid? We’ve seen what it does to steel in all manner of battery compartments but I don’t want it to ruin the aluminum as well.

Phosphoric acid? Some say it will only go so far before passivating the metal studs where the reaction then comes to a stop.

Finally, I know having a shop with an EDM (electrical discharge machine) can possibly electrically erode away the studs but I think that could get pricey. Plus, having the head and block together means I can’t exactly toss this in the back of my car at present. I also don’t want to do anymore disassembly at this point. In a worse case scenario – and lacking other options I’m not aware of – I’d have to destroy the manifold in order to remove it and replace it with a used one from… somewhere. I’m loathe to even write those words as its admitting that I will have failed. Ugh. As an aside, I also researched the marine-related forums such as the wooden boat restoration ones and came up empty as well.

Moderators: feel free to move this to the engine forum if it would be a better fit there. Thanks.

Comments on your part are welcome.


I think I would try placing a 1/4" drill rod into the holes and applying an air impact hammer (AKA jitter gun) to the end of the rod. You don’t want to mushroom anything but I’ll bet a little vibratory persuasion will break loose the corrosion bonds between what’s left of the studs and the intake manifold.

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I have an early MKVII engine that was rebuilt many years ago, but seized (due to rebuilder error, left a part out of the water pump). I cannot remove the timing cover.

Presumably the locating dowels are causing this.

What I am going to do next, I have tried variations on, and worked on other similar.

get razor knife sections, and hammer then down between, next, putty knives

This will cut gasket, chemicals (and metal, so must be careful)

I use ATF/turps mix as penetrant

I personally would be very reluctant to use acid on al alloy

Your post gives me inspiration to get that thing off

with the inlet manifold, at least it should be possible to machine the inner surface, if minor damage occurs

You may possibly have attempted this

above is why I remove every stud from a head, and coat with anti-sieze

It sounds like what I went through with a 140 engine my brother found in a field.
At the extreme frustration point, I had the weight of the entire head dangling from one stuck stud. Many cycles of heating with a propane torch and soaking with penetrating oil eventually got it loose.

The operative principle is wreck the cheap simple parts to save the important hard to replace parts.
Do you have the head off? If not, take it off.
You drilled out the studs 1/4", but you should continue to 5/16" diameter and to within 3/8" of the gasket face. Buy a good 5/16" flat end punch. Hang the head suspended down from the manifold and apply the oil and the punch and hammer to those short stubs of studs.

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To boil them out with Alum you need to have to arrange the bath and head so that the offending steel part is immersed in a saturated solution of Alum kept just at boiling temperature. iirc it’s about 200g Alum/l to saturate.

You’d need to have the head off, and suspended in a large enough pan, with any steel parts you want to retain either removed, or masked with some kind of heat resistant paint (It will attack the valve seats too) and not suspended in the solution.

To save time it would be best to drill out the offending studs, both as large a diameter as you can, and also through (so the solution can reach the back of the stud).

It would take a good while to dissolve the remains of 9 studs even if they were drilled out… days, I would think.

The immersed Al will also be covered in a black smut which is very hard to remove.

I would say that since the head has to come off, then it’d be faster to set it up on a mill and either drill or edm the studs to within a helix of their stubbornness.

EDIT: See http://www.jag-lovers.org/snaps/snap_view.php3?id=1380816154 for pics.

Maybe the manifold can be painted with something that will come off with paint remover but not let the oxide through? It will be very difficult to seal things up in there especially when you think about what’s going to happen when the solution gets down to the block, valve seats etc.
When the manifold is removed and the head off alum to remove the rest of the drilled out fasteners?

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Thanks for the replies, guys. And Mike Eck, I will try the air hammer trick to try and jolt the studs loose. If that’s still a no-go, then I’ll put this on the back burner for a few days – at least to clear my head. In the meantime, I have a local lead on a used manifold at a decent price so I might buy that as a backup spare. I’m thinking I’d then turn everything over to the rebuilders with a comment along the lines of, “Here, try and get this off. If you fail like I did and ruin it upon removal, then here’s a matching spare.”

As a side note, I’m actually looking forward to the day (though not with this car) when I can try out the process using alum. I occasionally mess about with 20s-30s English and American motorcycles and this seems ideal for removing sheared off studs in crankcases and gearboxes. I wonder why it isn’t more popular than it is? I have all manner of books on restoration over the last 30 years and none of them mention this process.

In my experience, the Alum process is only suitable for small alloy objects where something iron is stuck. It takes quite a lot of Alum to saturate even a pint of water. The part needs to be submerged in the Alum mixture, in a non-iron pan, and kept at a near boiling temperature for many hours. Eventually, the stuck iron piece will dissolve enough that it will loosen up.

I used the Alum process on one of the original small “toilet seat” covers from the spat of my XK120. The toilet seat cover needed to be re-chromed, but the iron hinge pin had welded itself to the alloy pieces after 50 years. I didn’t want to force the hinge pin out for fear of breaking the delicate alloy parts.

It took about 4-5 hours of cooking the toilet seat cover in the Alum mixture before the tiny hinge pin could be removed. The Alum did not damage the alloy parts except for leaving them blackened, which I was able to scrub off.

The chrome plating came out fine. I wouldn’t want to guess how long the Alum process would take to loosen the studs from a cylinder head.

Mike, I don’t think a larger stud would take any longer to remove than your hinge pin as it would only be necessary to dissolve enough of the outer circumference for it to become loose. Or am I missing something?

Back to the intake manifold:

As this is one of those items with dissimilar metals contact, minimal stud/ hole clearance, coolant seepage and throw in age as well, my takeaway from this is that if one doesn’t have a good reason to remove it, then don’t. If it is removed, then at the least, smearing the shanks of new studs with a decent anti-seize is a must. Future gearheads in-the-know will thank you. One could also drill all holes slightly oversize and press in off-the-shelf thin wall bronze sleeves sold as “oilite” bearings. That would really take it to the next level for the more persnickety among us.

The Alum only attacks the exposed surfaces of the ferrous material. That’s why drilling through a larger fastener speeds the process up.

It’s fast and easy if you’re boiling a broken screw out of a brass pocket watch… But then those screws are only about 1mm diameter.