Replaced the plugs last night and used an anti-seize (type 13, what I happened to have on hand) on them (never have done that on plugs on any car before--always done it by feel, even the XJ6L). Had my torque wrench set at 18 ft/lb. The first one I did it got hard to turn, but kept turning and the wrench never clicked. I got paranoid I was stripping out the threads so stopped and used a regular socket wrench. None of them really felt like they seated (like a hard stop) but they were tight to turn, just kept turning (just not 18 ft/lb tight)so just stopped turning them.

So needless to say, I'm concerned that I don't have them tight enough, yet afraid I'm turning them too much and I'm stripping them. Any insight/experience is greatly appreciated. I might try setting the wrench to 10 ft/lb and see if they'll click. I've got to assume that it's going to take 35-40 ft/lb to strip them, but I have no idea.

Help...

 

what is the range of the torque wrench you are using? I ask because if you're on the low end of it's range, they tend not to click. i.e. if it's a 'bigger' torque wrench, say it goes from 10-100lbs, they usually won't click, you sort of have to feel it change.
It's the only time I've really seen anyone strip an aluminum head out with a plug.

I have a smaller torque wrench (inch pounds) that does a great job for those.
Also the cheaper ones tend not to click well either.

Or you can just do the NGK seating method, turn it until you feel the washer seat, then tighten a quarter to half turn. A good method that will get you there if you can't get a torque wrench in there.

 

18 ft/lbs is the 'dry' torque- no anti-seize applied. Torque must be reduced when using any lubricant, possibly 30-ish %.

 

An excellent method, and far more consistent than a torque wrench.

One clarification though, NGK specify 1/12 turn on used washers. So, if the plug is used, then that needs to be accounted for.

 

is that 1/2 or a 1/12th turn you mean plums?

 

It'll be 1/12 as a used one is already crushed so you want to crush only a little more else you'll overtighten.