snug them down and barely past that
Changing plugs
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2
NO...
The shop manual spec is 11 lb-ft. Finger tight then 1/16th turn will be about 13-15 lb-ft, most plug maker's recommendation for taper seat plugs. Adding 1/4 turn will bring them up to 45 lb-ft or better--way too tight...
Here is a test I did using a "plug bore" machined into a block of aluminum alloy:
You can see that adding 1/6th turn (22.5°) required 15 lb-ft, 1/4 turn (90°) more took 47 lb-ft!
It is vital to properly torque the plugs on the 4.6L 2V, not doing so is what leads to the plug blowouts we hear about far too often.
I personally feel 11 lb-ft is too low for used heads with oily/carboned-up threads--and with the common use of never-seize (not recommended by Ford, the minimal threading was engineered to deal with seizing issues). These both lubricate the threads and make the plug easier to "back-out" under normal operation.
This is why I use and recommend 13 to 15 lb-ft, generally setting my wrench for 170 lb-in (14.2 lb-ft); though for a year or more now I have been using a torque-limiting socket:
This neat tool is calibrated to very accurately provide 20 N·m (177 lb-in, 14.75 lb-ft) of torque, no more and no less. Read more about it here.
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