If you have a melted coil pack, an improperly tightened spark plug is 100% the cause.

 

Damn! They were all fairly tightened when I changed it but thanks for that info. I still don't know why it broke off the first time. The first time I pulled my plug it was black/sooty which I saw you mentioned

 

What does a sooty coil pack mean?
This thread got me thinking; when I did the valve retainers a couple weeks ago, one of my plugs porcelain was a little brown and the coil pack was a bit sooty.

 

It doesn't work like that. The loose spark plug allows air to be drawn into the mixture past the threads. This leans out that cylinder, and the hot gases get past the threads and cook the coil pack.

The OP's plug did not suffer this kind of damage, note how clean the spark plug is (the shiny hex and clean top portion)

OP, it appears you have a lean condition in that cylinder. Anyone crafty that has a scanner which can read trim data can do what I call trim-balance and verify this.

This is very important. If your engine is ok, this will happen again and next time major engine damage can follow.

Anyone reading this should know with absolute certainty that your spark plugs are torqued to 24 ft-lbs. It is becoming one of the most common causes of engine failure.

 

Top is the first time the spark plug went bad. Replaced it and then the second spark plug was toasted.

 

Is the engine of f20racer boosted ?

 

not boosted.

Im still waiting for analysis on my engine

 

Redrumm, that plug wasn't even close to being properly tightened. Note the metal plug gasket has 0 compression, and the blowby of exhaust soot on the threads and the hex portion of the plug.

Same goes for second pic, exhaust blowby from a loose plug.

Get yourself a torque wrench, 24ft-lbs.

I will warn you now your threads may be torched. If you cannot achieve the torque without stripping, a proper timesert repair will be needed.

 

THIS. I can't even tell you how many cars were at the Dragon this past event where Bill and myself had to go back over and retighten plugs for people who had already "torqued" their plugs. It's very important to get full crush on that sealing washer. It will feel like you're stripping it out, but unless your threads are boogered from being undertorqued and torched in the past, eventually the plug will bottom out. Once you bottom out, THEN torque to 24 ft-lbs.

 

I have been tightening using a quality torque wrench set for 22 ft-lbs and simply stop torquing when it clicks. To be sure I understand, are you saying the correct way to tighten the plugs (OEM) is to NOT use the torque wrench, crank it till we "feel" the crush of the washer and THEN use the torque wrench? Does the resistance of the crushing washer exceed 24 ft-lbs so you need to do that first?

It seems like you can re-use the washers (reinsert the plugs) at least a couple of times.