I did this to show how you shouldn't install spark plugs in the Z... however they torqued in with the impact just fine and there was no damage. Also, others have done it on the forum and it is an industry accepted way to install plugs. I have already said that you could install them with less torque, but how are you going to know when the threads will strip out and the ceramic cracks unless you test to that level of torque? Besides, only one broke off and rebounded off the shop wall... lol