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torque setting spark plugs


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#1 lawn bowls

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Posted 20 April 2017 - 12:15 AM

this might be a stupid question does anyone know the torque setting on holden 6 spark plugs.if you over tight them it can cause detonation and other problems.



#2 hanra

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Posted 20 April 2017 - 06:14 AM

Care to explain?

#3 Dr Terry

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Posted 20 April 2017 - 07:04 AM

There are 2 types of spark plugs used in Holden 6-cyl engines. Pre-HQ (& XU1) engines use a plug with a metal sealing washer while HQ onwards use a taper seat plug.

 

Neither type requires a great deal of torque, however the washer seat type requires more torque on initial fitting to get the required crush for the washer. From memory the torque required is about 30-35 Nm, although I'd have say after 45 years + in the motor trade I've never seen a mechanic use a torque wrench to fit a spark plug. It's more a matter of 'feel'.

 

The taper seat type requires very little torque to fit (around 10 Nm). Not much more than just a 'nip'.

 

The most common error made is people over-tightening taper seat plugs thinking that they have washers. Once they've been in the engine for 20,000-30,000 km they are very difficult to remove, they often snap off.

 

Dr Terry



#4 Bomber Watson

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Posted 20 April 2017 - 07:45 AM

Im interested in the science behind how it can cause detonation.

#5 Lazarus

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Posted 20 April 2017 - 12:04 PM

It 'strangles' the spark plug if I remember correctly, kind of like a duck shitting all down your trousers while you're strangling it.



#6 arrimar

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Posted 20 April 2017 - 12:27 PM

It 'strangles' the spark plug if I remember correctly, kind of like a duck shitting all down your trousers while you're strangling it.


A duck..really? Cats yes but never had a duck do that.

#7 I'm a Red Motor fiend

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Posted 20 April 2017 - 01:10 PM

Why not go to your plug brands website and check?

#8 arrimar

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Posted 20 April 2017 - 01:46 PM

NGK data.

BP6ES (washer seat) 25-35Nm in cast iron 15-30Nm in alloy

BP6FS (taper seat) 15 - 25Nm in cast iron 10-20Nm in alloy

(1 Nm = 0.7375 lb ft)

#9 LS1 Taxi

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Posted 20 April 2017 - 02:01 PM

I wish I never clicked on this thread.

#10 lawn bowls

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Posted 20 April 2017 - 03:18 PM

just going on the ngk web site about over tighten spark plugs can cause detonation.



#11 Bomber Watson

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Posted 20 April 2017 - 03:25 PM

Just looked it up, not really much of a scientific paper there providing us with is it?

Looks to me more like a catch all "you cant sue us" type comment. 

 

1/2" ratchet, give her a nip, go have a beer. 



#12 lawn bowls

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Posted 20 April 2017 - 03:40 PM

i just had another look it says if its under tighten not fully seated heat transfer will be slow and cause pre ignition and detonation,so i got it wrong about the over tighten causes detonation.my apologies.



#13 Bomber Watson

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Posted 20 April 2017 - 04:08 PM

No it does say under over tightening that the same things can occur. 



#14 S pack

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Posted 20 April 2017 - 05:25 PM

I wish I never clicked on this thread.

If you hadn't made a post no one would have known. :stirpot:



#15 RallyRed

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Posted 20 April 2017 - 06:03 PM

going out on a very shakey branch here....and I'm pretty sure it would be bees dick stuff....but if Arnie cranked the plug in a few more turns...wouldnt it take up more cc's in the chamber...and increase the compression...and risk detonation.?

 

Cant imagine it ever occurring in practice though?



#16 S pack

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Posted 20 April 2017 - 07:00 PM

going out on a very shakey branch here....and I'm pretty sure it would be bees dick stuff....but if Arnie cranked the plug in a few more turns...wouldnt it take up more cc's in the chamber...and increase the compression...and risk detonation.?

 

Cant imagine it ever occurring in practice though?

Col, he'd snap the plug well before a few more turns. :)
 



#17 RallyRed

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Posted 20 April 2017 - 08:21 PM

yeah, thought so.....but 



#18 caterham2

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Posted 02 May 2017 - 08:16 PM

Has anyone checked with the RSPCA to see if they have heard about the phantom duck strangler on this forum? Should be easy to spot , got duck shit all down the front of his strides.



#19 ozyozyozy

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Posted 02 May 2017 - 10:26 PM

Over tightening can cause issues too.
We actually had a technical bullietin at a dealership i worked, for this reason.
its not a normal thing for a factory to come out and say in this way.
This was for a small diameter spark plug tho, caused them to stretch.

#20 big jack

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Posted 05 May 2017 - 05:13 PM

They also say the electrode should face a certain way in the combustion chamber for what ever reason, any one shed some light or spark lol on this?



#21 EunUCh

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Posted 05 May 2017 - 07:39 PM

Crikey :) , when did nipping up a plug become so technical ?

Have heard that you can "index" the plug to face one way or the other but how much difference it makes to anything might not make

all that much difference  at all ? , not sure , it could be a fable but vague memory recalls that they tend to have the sparky bit facing

the exhaust valve ,(i.e. the ground electrode facing away from the exhaust valve) .

 

Would take a bit of time to mark all plugs and then work out how much material needs to be removed off the taper or face in the case

of squashed seal ring type to get them all pretty close , then make a jig to modify the ones that need trimming , it might not make much difference at all but then again next time a set of plugs is pulled it might be worth a look at which ones face where and are the "cleanest" looking ?.....either that or buy a million plugs and find out which ones fit up pretty close .



#22 hanra

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Posted 05 May 2017 - 08:24 PM

I bought 16 plugs from super cheap auto and run each one through until I found 8 that indexed correctly without having to use shims. I just marked the insulator inline with the electrode on each one so I knew the position.

Edited by hanra, 05 May 2017 - 08:29 PM.


#23 LC-GTR-1969

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Posted 05 May 2017 - 08:26 PM

Crikey :) , when did nipping up a plug become so technical ?

Have heard that you can "index" the plug to face one way or the other but how much difference it makes to anything might not make

all that much difference  at all ? , not sure , it could be a fable but vague memory recalls that they tend to have the sparky bit facing

the exhaust valve ,(i.e. the ground electrode facing away from the exhaust valve) .

 

Would take a bit of time to mark all plugs and then work out how much material needs to be removed off the taper or face in the case

of squashed seal ring type to get them all pretty close , then make a jig to modify the ones that need trimming , it might not make much difference at all but then again next time a set of plugs is pulled it might be worth a look at which ones face where and are the "cleanest" looking ?.....either that or buy a million plugs and find out which ones fit up pretty close .

Indexing works- albeit small gains...

 

And you can buy washer kits to help index. My 6 took 9 plugs to index last time I did it, and that was without any special washer kit. With a washer kit 6 plugs would do it in a 6. 8 in an 8 and so forth. 

 

However, you will get more gains from side gapped plugs. I gained just under 1mph on drag strip with side gapped and indexed plugs over standard. To me thats about 5hp. Worth the 10 minutes of frigging around when you could pay 1k in porting to gain 10hp.


Edited by LC-GTR-1969, 05 May 2017 - 08:28 PM.


#24 lawn bowls

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Posted 05 May 2017 - 10:03 PM

for heat silver plugs are the best then copper plugs



#25 ozyozyozy

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Posted 05 May 2017 - 10:09 PM

Be more gain at a drag strip in setting the car up to launch harder, reducing 60ft time, that can be as simple as getting the tyre pressure correct.




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