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Old 04-01-2014, 02:34 AM   #1
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spark plug torque

Anyone feel that 22 ft lbs is excessive?
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Old 04-01-2014, 03:22 AM   #2
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Only for re-installed plugs - go to 19 ft lb for them.
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Old 04-01-2014, 09:56 AM   #3
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Wow, a "blast from the past!"

I haven't tightened anything to a ft-lb spec in decades.

Says 25 nm on the Beru box and that's 18.4 ft-lb, so yes 22 is excessive.
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Old 04-01-2014, 11:08 AM   #4
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How odd. The Bentley manual (page 3-30) gives spark plug torque as 22 + 2 ft. lbs. Notes "spark plug applications are subject to change". A copy of the FSM from 1998 also gives 22 + 2 ft. lbs. Wayne Dempsey's book gives 22 ft. lbs. too. Has Porsche put out a service bulletin on this?
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Old 04-01-2014, 11:12 AM   #5
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Quote:
Originally Posted by lkchris View Post
Wow, a "blast from the past!"

I haven't tightened anything to a ft-lb spec in decades.

Says 25 nm on the Beru box and that's 18.4 ft-lb, so yes 22 is excessive.
Spec is 22 ft. lbs. +/- 2 ft. lb.
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Old 04-01-2014, 12:08 PM   #6
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Bosch FGR 6 KQE box says 21 ft. lbs. I'm glad all the manufacturers agree.
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Old 04-01-2014, 12:30 PM   #7
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The only one that matters is Porsche: Spec is 22 ft. lbs. +/- 2 ft. lb.
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Old 04-01-2014, 06:29 PM   #8
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From the Boxster service manual as of MY 2005 - which usually means MY 2003 for engines:

Spark plugs Using new spark plugs Tightening torque 30 (22 ftlb.) Nm
Spark plugs Re-using old spark plugs Tightening torque 25 (19 ftlb.) Nm

The recommendation is to back off on used plugs.
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Old 04-02-2014, 11:45 AM   #9
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Originally Posted by JFP in PA View Post
The only one that matters is Porsche: Spec is 22 ft. lbs. +/- 2 ft. lb.
Porsche doesn't have much say in the specification of the crush washer the plug manufacturer includes with the plug.

I'll use the plug manufacturer recommended torque.
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Old 04-02-2014, 11:48 AM   #10
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Quote:
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The recommendation is to back off on used plugs.
... because the crush washer is already crushed.
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Old 04-02-2014, 01:37 PM   #11
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Porsche doesn't have much say in the specification of the crush washer the plug manufacturer includes with the plug.

I'll use the plug manufacturer recommended torque.
Perhaps, but they do have a very good idea on what it should take to get a correct seal on any brand of plug without damaging the threads in the cylinder heads.....
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Old 04-02-2014, 02:20 PM   #12
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May I point out that any five of you could torque that plug to what you think is exactly 22 ft-lbs, and no two of you would have acheived the same amount of tightness.

This was demonstrated quite effectively to me the last time I had my torque wrenches calibrated, when the tech showed me how your individual touch using the tool will affect results. Even though I could consistently get the same number on their meter, the tech consistently got a different result, and my buddy consistently got yet a third number. The variance between the three of us was about 4 ft-lbs at 50 ft-lbs, on a wrench with a range of 5 - 75 ft-lbs.

Also take into consideration the potential error present in the tool itself. When was it last calibrated? Is it a quality tool?

So, really, debating whether it should be 20, 21, or 22 lbs is pretty pointless. If, like JFP says, you go with the Porsche spec, your actual range of torque will likely be anywhere from 19 to 25 lbs, assuming a properly calibrated tool with average variance. And it will work just fine.
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Old 04-02-2014, 03:27 PM   #13
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And to add to the confusion, it depends on who uses anti-seize compound to the plug threads.
I believe that also "changes" the torque required to seat new or old plugs correctly.

I personally use anti-seize but there are a lot of people who just screw them strait in the head without any lubrication. That's great when installing the new plugs, but can become really difficult to remove when they have been in situ for 50,000 miles with a million heat cycles and no lube .....
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Old 04-02-2014, 03:30 PM   #14
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Originally Posted by JFP in PA View Post
Perhaps, but they do have a very good idea on what it should take to get a correct seal on any brand of plug without damaging the threads in the cylinder heads.....
They do indeed, but the plug folks recommend less than they do, which will not damage threads and be farther from doing so.

Yes, wrench calibration and operator technique certainly mean being "spot on" is unlikely.

VERY important is dry threads and reducing torque when reinstalling previously installed plugs. If someone just can't listen to those that make plugs, at least reduce the torque if you have to lube the threads, antiseize being lube of course.
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