Plug Torque Query

[chris86uk]

Because of the problems I've read about with the Modular V8 and plugs deciding to make their escape, I bought a torque wrench for the job. My Haynes manual says the correct setting for the plugs is anywhere between 7 ft/lbs and 14 ft/lbs. I decided to settle somewhere in the middle and go with 11 ft/lbs, but I can't believe how little this actually is.

I can't get my head around how anyone can actually NOT tighten the plugs enough and have them back out, am I missing something? Is it that people actually massively over-tighten, and damage the threads that way?

What I've read has just made me a bit paranoid, 11 ft/lbs feels barely more than finger tight. I don't want the 'jack hammer' scenario to happen and wreck the threads that way either.

Thanks for any advice!

Chris

 

[MustangChris]

you're missing something


ford only put in 3 threads on some designs of the heads (some got 6 threads) -- 3 threads holding in a combustion isnt much.

it took until late 2004 for them to put in 9 threads on the terminator 4.6s....

its not that the owners weren't tightening them enough, its that the threads weren't giving enough hold to keep the plug in against the engine's power.

additionally, on aluminum heads you can pull the threads out by over-tightening them.... which simply added to the problems.


use anti-seize. it can help act as a lubricant and will give a more accurate read on the TQ wrench.

If 11#s wasnt what makes you feel safe, max it out at 14#. (make sure you're reading your wrench correctly, as well.)

 

[duff daddy]

Aluminum is soft, low thread count, also remember aluminum will heat soak, this will have a good bit of expansion and contraction.

 

[chris86uk]

Thanks guys.

Do you think 11 ft/lbs is enough even if I only have 3 thread heads then? I suppose checking the torque periodically would be a good idea.

 

[vermilion]

I use 12. I dont know exactly how much threads i have but sure have a bit of boost. If you dont jerkules the torque they last awhile. Only service the plugs while cold.


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