Spark plug torque - very technical

[carbold]

Hi guys
just wondering, I don't have that spark-plug thingy you can use with a torque wrench to torque properly, so I always do it kind of randomly, a quarter of a rev from when I start feeling it hard to turn, so what do you people do?

 

[littleredrooster]

For new plugs, NGK recommends tighten to finger-tight then +three-quarters of a turn (I think!)

 

[(RIP) Kaister]

1/4 turn on a new crush washer - 1/8 turn on an old one.
1/8 turn on smaller taper-face plugs.

if you have to ask or use a torque wrench, then i'd suggest being VERY careful.
Always start the plug by hand, using a v.small dab of anti-seize AND wd-40.
Only torue up for the last turn - wind it in by hand / socket.

I've seen a few broken spark plugs by people 'pulling' the wrench out of round, not turning it concentrically - easily done.

Phil

 

[andy malton]

plugs

If you want to use a torque wrench - Weld a nut on the end of the BM* thingy

I think it is 5nms - but will check - never overtighten

Not much - the technical answer

Para

I think you will find that it's 20nm for the plugs.I have never had a any problems useing this setting,I always put a little copper grease on the threads first.1/8 of turn from when the crush washer first seats is not enough IMHO.It,s not the washer that holds it in there it's the threads.A new plug will turn at least once from when the washer seats,then torque it to 20nm.Andy

 

[Mick Fagan]

For my 1100 I bought a thin walled ½" drive socket of the correct size for the small plugs in this machine.

I then had a mate turn it down so that it fitted down the small shaft that the plugs go into.

From there it's a snap to torque the plugs correctly. I know from experience that the plugs seem to turn more than a ½ or ¾ of a turn before they are correctly torqued!

The other good thing, is that because the trimmed down socket is quite small, it is able to reside in the under the seat toolkit.

Mick.

 

[BiG DoM]

BMW secifies 20Nm - I use the 'elbow torque wrench'!

 

[KOTM]

Thought about the welding a nut on the end, and also about buying 'specialist tool', then thought some more.
Go to local DIY store and buy a big RAW bolt that just fits inside the round end of the B*W supplied plug spanner. Tighten said RAW bolt until it grips the inside of plug spanner. Then use conventional torque wrench and socket on your 'newly modified' plug spanner. Go to pub with time and money saved.

 

[carbold]

So is my understanding of english still crap or we didn't get anywhere??!!!
We could modify the standard spanner (many good ideas here)but then the torque wrench wouldn't be accurate at low torques, or we could turn 1/8, a quarter, a half, 3/4, or use the "just the flick method", always considering different cases for new and old plugs....

Given the situation may I suggest a new method?

- Grab the plug and smear some copper grease on the thread
- Hold steadily and fart on it: this will make the grease reach the correct viscosity
- Screw the plug until it gets really hard (!)
- undo the TPS and kick it
- back to the plug, get ur partner and let her tighten the damn thing
- reconnect the spark plug cap but do not forget to spit in it: this will clean your mouth and make you feel young again
- If you are using new plugs, get rid of the washer

 

[(RIP) Kaister]

http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp?nav=31300&country=US#installing

and exactly the same figures here:


http://www.championsparkplugs.com/search_char.asp?seenWarning=1&manufacturerID=

Plug torque settings

It is essential to tighten a spark plug to the specified turning angle or torque setting. This is for a number of reasons, over tightening can cause;
1) Damage to the threads in the cylinder head (especially aluminum heads).
2) Damage the threads of the spark plug.
3) Damage the internal seal of a spark plug allowing combustion chamber blow-by.
Under tightening of the spark plug can cause plug overheating and possibly pre-ignition. This is because one of the primary purposes of the spark plug is to remove heat from the combustion chamber, it does so by transferring that heat to the engine head. If the plug is not properly tighten it will not have sufficient contact with the head to transfer that heat. Proper tightening procedure is described below.

Screw in the spark plug finger tight until the gasket meets the cylinder head. Then seat the plug/gasket with a torque or turning angle wrench as specified in the chart below.

Spark plug type -Thread Diameter- Cast Iron Cylinder Head (lb-ft.)- Aluminum Cylinder Head (lb-ft.)
Flat seat type -(with gasket) -18 ø mm- 25.3~32.5- 25.3~32.5
-14 ø mm -18.0~25.3 -18.0~21.6
- 12 ø mm- 10.8~18.0- 10.8~14.5
- 10 ø mm 7.2~10.8- 7.2~8.7
-8 ø mm -- 5.8~7.2
Conical seat type (without gasket)- 18 ø mm -14.5~21.6- 14.5~21.6
Conical seat type (without gasket)- 14 ø mm- 10.8~18.0 -7.2~14.5

definitive answer.

Torque is independent of size of wrench or bolt head size.
Torque is calculated at the AXIS (c/l) of the thread.
Settings are specified as clean and lightly oiled threads - NOT dry.

Phil

 

[Keith Chapman]

So what is 7.2 - 8.7 ft/lb when converted to elbow/flick

 

[carbold]

Keith that is exactly the point I was trying to make...
I think I'll go for 1/2 turn 'cos I FEEL it's the right torque

 

[carbold]

Thanx Para
remember you need a fart for EACH plug, cheating is not allowed