Hive-Motors Contest - Broken spark plug during replacement

Hello all Hive community, by now you know who I am and my passion for engines and work performed independently in my everyday car.

I am a happy owner of a wonderful Alfa 75 2.0 Twin Spark, and all maintenance I manage to do myself in the backyard (sometimes when I get the unexpected even on the side of the road!).

Source: Author

With this new thing I learned I'm entering the @Hive-motors Anniversary contest.

As in all situations there is always a first time, and that one marks and teaches.
A lot.
Let's get to it.
Routine maintenance of the ignition system:

• Replacing Spark Plugs,
• Replacing distributor caps.

Source: Here

• Replacement of distributor brushes

Source: Here

Very simple work that is completed in 30 minutes by working quietly and singing!
I prepare all the instrumentation:

• Ratchet with 16mm spark plug socket
• Torque wrench
  Perfect, nothing is missing, I already got the parts from the store so we can go!

I start the engine for a few minutes so that the head warms up a little and the spark plugs can be unscrewed without any problems.

So that I don't mess with the wires, being a Twin Spark I have 2 spark plugs per cylinder, I unplug one pipette at a time and replace the spark plug.

I start with the 4th cylinder, the farthest and most uncomfortable as a position to work.
I replace the first spark plug and proceed with the second one in the 4th cylinder.

I tighten the spark plug with the hand wrench and then take the torque wrench set at 2.5 Kgm (25 NM) I start to tighten the spark plug but it seems to be turning in circles....

How is this possible?

I try to unscrew it and when I pull it out, the threaded part remained perfectly screwed to the head!

At that very instant I completely lost my mind. I closed the hood and went to bed.

Early the next day I went to a well-stocked tool shop is I bought special extractors. These tools are very similar to a drill bit but the helixes are upside down: to screw them in you have to turn them to the right (or counterclockwise) this way, having sharp edges they lock on the piece of metal and you are able to unscrew them.

Source: Here

Once I recovered what I needed I went home and removed the broken spark plug part... So far nothing complicated, I take an old spark plug and try to reassemble it, result: the thread is ruined!

This the "corpse" removed from the head of my beloved Alfa!

Source: Author

Whaaaat?

Did the thread on the head get ruined?
Let's hope not!

That's when I phone my trusty mechanic who tells me exactly what I need to do: buy a 14x1.5 thread tap and some copper-plated grease.

Source: https://www.voelkel-shop.com/it/maschi-a-mano-serie-a-due-parti-din-2181-hss-g-mf.html

Once I bought these components, his explanation was peremptory:

• Put a screwdriver inside the spark plug hole;
• Engage 4th gear and keep the car moving until you see the piston going down;
• Remove the screwdriver
• Take the male with the male turner and fill the male well, in fact very well with coppered grease and start rethreading.
• After 3-4 turns maximum pull out the male, remove the grease that will have all the residue of the old threads and repeat the operation until you reach the end.
• BE CAREFUL, when you feel it sticking don't turn yet, you are on the top of the piston, if you insist you will make a hole!
  Very calmly and a little agitatedly, I started to do the job and within 10 minutes I had it done, put the new spark plug back in and it screwed in perfectly even by hand and tightened it with the dynamometer.
  Happy as a child in front of the Christmas Tree, I also changed the other spark plugs and off I set my beast running like a Swiss watch!

This setback taught me one very important thing: self-confidence!

My mechanic knew perfectly well that I was able to do the job, but I wasn't so sure, so much so that I was almost tempted to take the car to the mechanic to have him do the work; instead, by plucking up courage and following step by step what the mechanic told me, I managed to solve the problem with the expense of €30 of the male kit, the spark plug wrench and the coppered grease.

Congrats to myself for such an operation!