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Spark Plug Gaps


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#1 happydude2012

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Posted 21 July 2018 - 01:12 PM

Bonjour la class

 

quick musing on spark plug gaps

 

is setting the gap a definite have to, if so does anyone have a link to a useful resource? lots of trashy "I reckon" stuff online but some idea of what to do and why from a "hexpurt" would be very valuable.

 

thanks



#2 Cooperman

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Posted 21 July 2018 - 01:56 PM

Set spark plug gaps to an accurate 0.025". It's a 'must do'.



#3 andyapanel

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Posted 21 July 2018 - 02:04 PM

Haynes has all relevant info.



#4 happydude2012

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Posted 21 July 2018 - 02:44 PM

silly question, can i use my valve clearance feeler for this or do i need the swanky spark plug end bending tool thing? if there even is such a thing?

also, what type of spark plug do you reccommend?



#5 Dusky

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Posted 21 July 2018 - 02:51 PM

I run no gap, i only run brisk multispark plugs (a true multispark plug,not a 3 electrode plug) after seeing the dyno result on my own cars. Worth their price imho.

#6 gazza82

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Posted 21 July 2018 - 02:51 PM

Normal feeler gauge is fine. You should need to bend them often. Unless you drop it and ram it closed! (Oops!)

Tapping gently closes them

#7 mini13

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Posted 21 July 2018 - 03:05 PM

if your completly without anything to measure them, the thickness of a hacksaw blade is not far off.



#8 racingbob

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Posted 21 July 2018 - 03:05 PM

I run no gap, i only run brisk multispark plugs (a true multispark plug,not a 3 electrode plug) after seeing the dyno result on my own cars. Worth their price imho.

did you compare to ngk plugs on dyno

#9 Ethel

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Posted 21 July 2018 - 07:18 PM

The bigger the gap the stronger the spark - assuming your ignition is up to the job. 25thou is the figure for points, electronic ignition might manage up to 40thou but 32thou is in Rover's books.



#10 Dusky

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Posted 22 July 2018 - 12:28 PM

I run no gap, i only run brisk multispark plugs (a true multispark plug,not a 3 electrode plug) after seeing the dyno result on my own cars. Worth their price imho.

did you compare to ngk plugs on dyno

The mini was VS ngk plugs, the mustang was VS AC DELCO plugs

#11 racingbob

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Posted 22 July 2018 - 02:25 PM

I run no gap, i only run brisk multispark plugs (a true multispark plug,not a 3 electrode plug) after seeing the dyno result on my own cars. Worth their price imho.

did you compare to ngk plugs on dyno
The mini was VS ngk plugs, the mustang was VS AC DELCO plugs
what was the difference on the mini in hp and what brisk do you use. the cone lookìng brisk I tried coil couldnt cope and drove like 998

#12 Dusky

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Posted 22 July 2018 - 05:56 PM

I run no gap, i only run brisk multispark plugs (a true multispark plug,not a 3 electrode plug) after seeing the dyno result on my own cars. Worth their price imho.

did you compare to ngk plugs on dyno
The mini was VS ngk plugs, the mustang was VS AC DELCO plugs
what was the difference on the mini in hp and what brisk do you use. the cone lookìng brisk I tried coil couldnt cope and drove like 998

The difference in hp was negligible , 2 HP if I recall right. Torque curve was a lot smoother,and higher from low rpm.

Dr14zc if I recall right, I should take a look in my paperwork,its a few years ago now

#13 racingbob

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Posted 22 July 2018 - 06:19 PM

I run no gap, i only run brisk multispark plugs (a true multispark plug,not a 3 electrode plug) after seeing the dyno result on my own cars. Worth their price imho.

did you compare to ngk plugs on dyno
The mini was VS ngk plugs, the mustang was VS AC DELCO plugs
what was the difference on the mini in hp and what brisk do you use. the cone lookìng brisk I tried coil couldnt cope and drove like 998
The difference in hp was negligible , 2 HP if I recall right. Torque curve was a lot smoother,and higher from low rpm.

Dr14zc if I recall right, I should take a look in my paperwork,its a few years ago now
what ignition was you using. yes those the plugs I tried bit had no go to it brisk said for better ignition cars

Edited by racingbob, 22 July 2018 - 06:23 PM.


#14 A-Cell

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Posted 22 July 2018 - 07:24 PM

The flame spread from the kernel (initial igniting of fuel air mixture) from these multi spark plugs is unlikely to be suited to the A series head as this was developed using single j type electrode.
The standard cylinder head was designed and developed to use the single electrode (old fashioned) plug.
Gap of 0.025 inch for contact distributor, 0.032 inch for electronic ignition.

If the gap is too small then there will be less air/fuel between to be ignited, too large a gap and the spark will be weak and ignition of the mixture poor and late.
So as Cooperman said correct gap is very important.
It only takes a few extra minutes to correctly gap plugs before fitting.

#15 spin

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Posted 22 July 2018 - 08:52 PM

A wire gauge  not a feeler gauge was the standard when leaded fuels were used

& plugs were cleaned and gaped more often.  you will not get a correct gap

on a worn plug with a feeler only with a wire gauge.

 

One of the wire types courtesy of Halfords

Attached File  gap gauge.tiff   143.64K   12 downloads






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