SII Head Stud Broken

Well I have been adding penetrating oil, heating with a propane torch and using a long breaker bar with about 3 ft arm but have not been able to remove the plug. I also tried a 1/2 impact wrench but did not budget. At this point I have decided to remove the engine so I can get better access.
Plan is to continue to spray with penetrating oil, and heat and then try a much longer arm and hang a bucket of bricks or similar from it for a few days. May also try renting a 1" impact wrench for a bit more oomph (technical term).

Any success stories of people removing this plug would be helpful at this time as it feels like I am banging my head against a wall :disappointed:.


Worst case you could drill, and carefully cut out the plug, cut just short of threads, crack it out with a punch, or cold chisel.

All I can add is that I’ve been told you can sometimes break a fastener loose by first trying to move it opposite the rotation you would use to loosen it. I don’t see why the same wouldn’t apply to the plug in question.

More specifically, drill a half inch hole in the center of the lug. Cut with hacksaw blade, dremel, mini grinder, or whatever, an “x” just to the threads. Then take a punch, and tap hard next to the drill hole on the remaining wedges. One will cave in, the rest will pull right out. It’s not as hazardous as it sounds.

Note this is a screw in steel plug (see earlier photo) and not the normal freeze plugs, so it is not possible to knock it out with a punch. Cutting and taking out the parts is a last resort option if the 7/8" hex key rounds off, but hopefully it won’t come to that.
Got to get the engine out first which is in process, but some bolts have not been touched in 50 years so taking a while to get stuff off, like the exhaust.


Jay, yes, I know it is the screw out plug. It can be drilled and parted out.

My fault, I misread your response. I saw the “One will cave in, the rest will pull right out.” and thought freeze plugs, but you were talking about the parts of the steel plug. Its been a long day :sleepy:

Hi Jay…have you considered welding a nut onto the plug…the heat could possibly break the seal and give you a better head to fix a tool to undo…Steve

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Ingenious. Apart from the fact threaded rod is normally mild steel I don’t see too much of a problem if the gasket doesn’t blow medium-term. Maybe there’s a new market out there for a high tensile ‘repair stud’. :slight_smile:

The socket ( as opposed to hex head ) plugs I have seen were brass.

Grade 5 and Grade 8 threaded rod is readily available from most any fastener supply store…

After a couple of weeks of penetrating oil and heating, the plug finally came free with the impact driver. Unfortunately part of the plug broke off while it was being removed so I will need to locate a new plug when I put it back together. Are these available anywhere or would this need to be custom made ?
Now I have the plug removed I cleaned out the debris and can see the remaining part of the stud that broke. It is very close to being broken off flush but I think there may be enough to be able to weld a nut or something on so I can try to extract. I am going to keep spraying with penetrating oil for a week or so and maybe add some heat from a propane torch. At least with the engine out I have a lot to work on while I’m waiting.



Congratulations. Glad to hear it finally came out.

I would put a dremel or chisel on that and see where the steel is. Hopefully there is enough to weld a bolt onto!

Monte is a very smart Patent Attorney and very creative, I worked closely with him and lent him my revealing gun drill for the studs, I highly recommend his method.
Mike Moore

The threaded boss was to take a heating element made by the Bray electrical company UK. I expect it will be a standard British thread of some sort. Can you work out how many threads per inch there are.?

I would grind that flush, so that there is shiny steel…if you choose not to drill from above;

place a thin copper washer to prevent welding stud to block

sit a steel washer on top, and mig the stud to the steel washer

mig a nut to the steel washer, and while its still very hot, wind it out

well done getting that plug out

Why bother…


This is another stud. Not the one to the left which is what I found a few weeks ago.
The insert has no shoulder which might partly explain why it didn’t take torque the way the others did.

The slots running vertically (in this photo) , between the cylinder walls , are they from factory ?


Yes, the last XK blocks (XJ SIII) were slotted between the liners as the blocks tended to crack between them. They flow coolant.
My head is on and I’ll finish it off tomorrow. Hopefully that will cure everything.