No luck with an extractor - I am using a 3/8" square type couple days of penetrating oil soaking. I will say I've been very careful with force here - light taps to seat the extractor, torque wrench to turn - and I can tell I'm not putting the same turning force I needed for the rest of the plugs. Maybe I should just give it the beans but I don't want to break the extractor

Perhaps give up and drill. I have clear access. I've had good luck with this approach with fasteners - size the drill carefully to leave a thin wall of thread.
But this is my first broken spark plug rodeo - is there blatant stupidity here I am not aware of?
Inspection shows the piston is pretty far down in the stroke so that's good

Suggestions on how I can clean the cylinder afterwards? *Perhaps I'm being too optimistic asking that question

 

Many ideas will float in.

Mine was a XK 6cyl, and my own stupidity was the cause.

I eventually drilled, and the drill bit was liberally coated in Wheel Bearing Grease, I know, but it was the 70's and wheel bearing grease was sticky and tacky. Slowly increased the size, and SLOW speed on the drill.
Got to point the remaining casing was easily collapes and removed.

Cylinder junk, easy. All sparks out, coil lead in my pocket, and wound it over for 5 seconds at a time, 3 times. NO specific, just what I did.

Sparks back in, coil lead in,and started it, all good, still running today.

BUT there are LH drill bits these days, never used them, maybe a good idea to look at at??
The grease is still a must in my opinion.

 

Ah that is great thinking on the left hand drill bit - I like that! Gives the massive amount of luck I currently have a chance to be good.
Thank you!

 

LH drill 100%. As Grant (turn and bow to the Southern Cross at the mention of the Great XJS Prophet's name) said, start small and slow, taking GREAT care to centralise the first drill. Use grease. Then in small steps increase drill size. Usually the remains will unscrew with the drill action as you get towards the largest size of drill.

I VERY strongly suggest a light coating of nickelslip grease on all plugs when new ones refitted. I have found copper ease will not do much, but nickelslip allows far higher temp performance. Costly, but a tin will last you and your grandchildren! eg:

https://next.henkel-adhesives.com/us...71/453790.html
or
https://next.henkel-adhesives.com/us...71/453790.html

I wipe a bit on with a screwdriver and then with a bit of garage paper wipe it into the threads. If you have not got one, a thread chaser is a good idea once you have drilled out the plug. Also use it on ANY plughole that the new plugs are reluctant to start into.

 

Biggest problem with drilling out isn't the metal it is the ceramic. In the past I have used a piece of vacuum hose on a garage vac whilst drilling, then using it whilst simultaneously blasting in compressed air - make sure the valves are closed !!! - accept that you won't get it all - a borescope will help the confidence level that you have got 99% the ceramic is the stuff you don't want in the cylinder. Don't get paniced and also do not drill too deep or make sure the piston is well out of the way, but that really needs checking the cam lobes and that is a whole ball of work that is no fun at all.

You can get kits specifically for rethreading plug holes if you end up with gnarled up threads so don't lose hope and think the head needs to come off unless you're into some serious self abuse ...

Chances are it was over torqued or it got wet, that leads to galvanic corrosion as the head and plug are different metals, this kind of corrosion can be strong as welding. Persisting trying to undo it may lead to galling and that will tear the threads out anyhow, you may get lucky with the left hand drill. Don't underestimate the power of a select amount of focused heat.

Never never never pressure wash or even hose a V12 unless you're going to meticulously dry every crevice in that valley and 100% follow Greg's advice on the nickelslip but reduce the torque appropriately since the torque specified is for dry threads and the plug seat is tapered so you'll get them in but you sure may not get them back out, use a torque wrench too - don't go 'that feels about right' they really don't need much. I generally knock 25% off the torque but see if the stuff you buy says anything about this.

A Footnote - something occured to me - your plugs I am sure are tapered seat, you must verify because if they are you must under no circumstance drill into or violate the seat - no amount of thread repair will fix that - I'm not even sure if the kits for rethreading plugs can handle taper seats - might be worth doing some digging before committing.

 

i had some success in the past by using shop vacuum connected to a brake bleeder tube and air can spraying beside that. I got all of it out like that. Borescope to verify definitely.
the comment about making sure valves are closed is something which didnt back then even came to my mind but is a good hint.

 

Drilled to 7/16 no luck. Next size I have is 15/32-I do not have tooling to measure how close that would be to getting onto the head but eyeball close. Letting it soak and time to … think… the extractors I have are useless garbage

 

Hi Thom,

You have received a lot of really excellent advice.

Thinking about your next step in drilling, 15/32 in. = 0.46875 in. The minor diameter of your 14 mm x 1.25 spark plug thread is 12.339 mm = 0.4858 in. So, if your drilling is perfectly centered in the plug base, if you drill with the 15/32 bit you will have a total of 0.01705 in.of spark plug base thickness remaining, or half of that per side, which is 0.00825 in. This is less than 1/100 inch of thickness.

In other words, if your centering is off by even 1/100 inch, you will damage the threads in the cylinder head.

If it were my engine, I would not drill any farther. Instead, I would buy some better extractors. The type Champion recommends is square with an extra sharpened flute along each edge, like these:



The hypotenuse of a 3/8 in. square extractor at its widest point is 0.53 in, which means it should fit snugly in your 7/16 in. (0.4375 in.) drilled hole, but a 7/16 extractor might work without extending so far down into the cylinder, posing less risk to the piston.

The article at the link below shows Champion's recommended method:

How to Remove a Broken Spark Plug

I have had success using this type of extractor. The method that has worked for me is to flood the plug base with a good penetrant at least overnight or for several days (Champion says at least a few minutes - of course longer is better). Install the extractor until it grips the spark plug base firmly. Apply counterclockwise force until you are afraid of damaging the threads. Relax. Repeat. Relax. Repeat until you feel the plug base just begin to turn. Relax. Apply more penetrant. Twist a little more. Relax. Apply more penetrant. Repeat until you can extract the entire base. Use a thread chaser or spark plug tap on the cylinder head threads as Greg advised.

If you use new Champion spark plugs, it is probably OK to apply a small amount of nickel anti-seize compound to the 1/3 of threads closest to the plug base, as Greg advised, but do reduce the torque as Ben advised. If you use NGK spark plugs, NGK states that no anti-seize should be used with their plugs due to the trivalent plating, which renders anti-seize redundant and makes over-torquing too easy. Remember that the junction between the spark plug threads and cylinder head threads is the ground path for spark, and anti-seize compound is a weak conductor of electricity, so you want at least most of the threads to be dry metal-on-metal.

As BenKenobi might say, "May the force be with you."

Cheers,

Don

 

Don
Thanks for that really important post; I had not heard of square extractors, but they are obviously far better for this job.
Not that it matters greatly, but the taper seat is also an earth path, I think. However, as you say leaving a few threads unntouched is a good plan; but at the top not the bottom of the threads is safer I think.

 

I like that Champion set up.

My penetrene, AKA The Brew, is 50/50 ATF and Diesel Fuel. Never, ever had something NOT free up. TIME, hell yes, and a FULL beer fridge are required items.

I have always used NGK, and Copper Eaze smeared on the thread, NEVER used a torque wrench on spark plugs. Common Sense from the Good Old Day (50's and 60's) s, "once the taper seat contacts,, a VERY SLIGHT oomph with a SHORT bar on the socket, done deal. Taper seat plugs DO NOT need to be Gorilla tight, that is just Gung Ho stupidity to me.

Take time, do other things, and it will come out.

 

May the force be with you indeed.

The only time I've ever see them fight this much is if the gorilla that put them in cross threaded this one, I wouldn't hold out much hope of undamaged threads, I think they're already done.

If I were you I'd be planning for one of the specialised rethreading tools, and make sure you get one that suits taper seat. If you do go down this path do not cheap out, go for something like these people supply -> Time-Sert these are a lot better than hellicoil

It's a pity you can't run a bead of weld inside the bit you drilled, not only would that shrink what is left but it would shock it thermally in a big way - this is a standard way to get bearing outer races out.

A last option is also not a cheap one - adjustable reamer - but again do not buy cheap junk. this way you can keep stepping up the diameter until you see threads breaking through as the origins, most of my bad experiences with these came from India. If you go this route they can be turned only one way and don't take big bites / cuts - and keep it square to the hole but I think this one is obvious

 

Might want to practice this

 

Thank you all, your advice has been my only hope!
The square extractors I have are duralast (auto parts store brand) posting this so folks know to avoid them - no bite at all and their "cutting edges" already rolling over from the most minimal of torque they did hold. I will gladly pay for premium quality extractor if I had confident recommendation?

The only welder I have now is stick and if you evaluated my skills - well lets just say only imperial stormtroopers are so precise. I don't have an acetylene torch but do have plumbing map gas and a mini butane (and a very healthy fear of fire, had a house fire 3 years ago) so I have not considered heat yet? Thoughts?

And lets say I need to go to the worst case.
Thank you for the link to the Time-sert - I read an older post that 14mm x 1.25 is the correct kit?

I really appreciate all the help here, I am confident I will have a fully operational V12 at some point in my future!

 

I ran across these extractors after I posted last night. Mayhew is an American supplier to industry of striking tools and other types of tools. I have quite a number of their chisels, punches, pry bars, etc. Some of their tools are manufactured in Asia, but many are made in the U.S.A., as this set is claimed to be. I ordered a set of these extractors for myself last night and hope the quality is up to their standards of fine-quality tool steel. They're supposed to arrive today:



By the way, while I'm thinking about it, harryepstein.com is a company that specializes in selling U.S.-made tools, and I first learned about Mayhew tools at their website.

Cheers,

Don

 

Here's what NGK has to say about anti-seize compound:

5 Things You Should Know About Spark Plugs

Cheers,

Don

 

Don
First apologies to the OP as this is getting a bit off topic!
First as to plug tightening: for all who are not sure, all it needs is just up to where it stops naturally without effort, and then a small extra twist of about 3° of turn, no more. Just a little firm effort of the wrist. Most mechanics give it far more than this. Once before retirement, I changed a set of plugs on my car and the mechanic who had last replaced them (who was excellent and knowledgeable) had omitted to finally tighten the B6 plug, which was loose in its hole, the car ran perfectly! Plugs on an HE do not need to be much more than finger tight.

I think anti-seize advice such as from NGK applies to almost every engine except the HE V12. I say this because I believe the heat and awkward location deep in a hole, plus the very hot general area in the V where airflow in all but carefully modified cars is poor, means factory coatings break down. I have never had any other car where this sort of precautionary treatment has been needed; but it is on (at least) my car's engine. I have mostly used NGK plugs on the car, too. FULL DISCLOSURE: The great Roger Bywater of AJ6 Engineering fame agrees with you and NGK and not me! But my experience with my engine has been that nickel slip (and not copperslip which cannot stand the heat) does make plug removal far easier.

I once did insert plugs with no anti-seize and my heart was in my mouth when I changed them next time. Each came free, needing an extension on my tool leverage, with a CRACK like the crack of doom; but luckily no damage. Nickelslip-ed plugs always seem to come free with far greater ease.

Thanks for the Mayhew Tools link; mine are also on their way, you cannot be under-prepared!

 

Grant
My favourite is 50/50 ATF and acetone, Magic!

 

Hi Don,
Thank you for the link for the Mayhew extractors. I've got a set on the way - arriving tomorrow I'll report back.
And I'll give the ATF+acetone mix a go as well.

 

Success!!!!!Thank you all for the advice! Now time to finally make progress!

 

And by the look of that the threads are fine - result - now go get a beer or three and enter a lottery ...