Cracking Spark Plug Porcelain Problem

[unique1]

Im having this annoying problem on my 26/30 at the moment and i originally thought it was a one off problem and its happened on 3 different sets of plugs now.

The porcelain on the top of the plug keeps cracking away. It looks like its starting to crack from the top down. I assume its heat related but the motor is running with no coilpack cover, afr's are mid 11s and pretty conservative timing numbers too, its only running a pair of stock gtr twins and previously ran a single gt3076r as well. Its got stock 26 coilpacks, and ecu is an Autronic smc. Im also making sure i dont tighten the plugs too tight too as i thought that was possibly the cause, so i have got 2 different people to install them and they all have same problem. I cant remember what cylinders it did last time but it was on 2 of them and this time i found the worse cracked one on cylinder number 1 and then the other on cylinder 4, i dont know if its happening on the same cylinder each time.

any ideas whats causing this? anyone had the same issues? These are BCPR7ES ngk's too

heres a few pics....

[The Dan]

Whoever is installing the plugs/coil packs is breaking them.

They don't just randomly crack like that. They are either being installed incorrectly, there is a problem with the spark plug socket being used, or the coil packs are being pushed down too hard.

[gotRICE?]

They must be done tight!

From memory you only need like 20 foot pounds (or nm i cant remember). Its not tight at all!

[femno]

Damn its not that hard to keep the socket straight on the plug...

Maybe get yourself one of those special spark plug sockets with the rubber insert to prevent cracking of the plug.

[unique1]

lol ive done about 500 spark plug changes before and never had an issue, i have done them for the past 5 years on the previous rb26 and no dramas ever on all my cars. Used the same tools and all so who knows.