Author Topic: Spark Plugs?  (Read 829 times)

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Offline earlbrown

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Re: Spark Plugs?
« Reply #30 on: August 08 2018, 01:01:41 PM »
Spark plug heat range has nothing to do with coolant temp, head temp, or cylinder temp.

It's just a description of how thermally coupled/decoupled it is from the 'cold' cylinder head.   A hotter plug has an electrode that's hanging out like a big ass heat absorbing heat sink.  A 'cold' plug has a very short projection.  It's just a description of the physical layout.


The only reason the adjustability is there is to fine tune around the exact engine and usage.  Too cold, and the plug can't get got enough to burn off the carbon. Carbon is conductive, so as soon as a path from the center electrode hits ground, the plug is shorted and can't fire.   Too hot, and the spark plug suddenly starts acting like a glow plug.  Also not good.


The window is pretty wide between those two extremes.   Since we're hotrodders and push our engines to around double the factory HP, the window gets narrower  (and spark plug QC becomes much much more important).


Picking out the heat range is easy. Put in a new set of plugs, kick the shit out of it, pull the plugs and look at the first few threads. You only want a couple of threads looking dull and 'burnt'. If 6 or 7 threads are obviously color changed from heat, you need a colder plug.


 There should be a color change band right in the curve of the side electrode.  That show timing, but this thread doesn't pertain to timing....

'87 GN - 4.2L SFI Turbocharged innercooled V6 - Chrome valve covers - supra pump - 14" K&N - 52mm throttlebody - rocker shaft supports -  1/2 intake spacer - TB coolant bypass - 3" ATR exhaust tip - Alum intake pipe - NOS timing cover - chip - relocated charcoal canister - CR42's - stock

Offline Scoobum

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Re: Spark Plugs?
« Reply #31 on: August 08 2018, 01:11:15 PM »
43's worked fine from idle to 28 PSI. I have a friend that wrenches on a Super Stock car. Think it runs 9's and is NA. On back to back dyno runs changing the gap made no difference in HP.
109 235 Cubic Inch Stock Stroke Balanced Rotating Assembly
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6.72 at 104.67-25 PSI

Offline nocooler

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Re: Spark Plugs?
« Reply #32 on: August 08 2018, 01:46:00 PM »
http://www.ngksparkplugs.ca/tech-info-spark-plugs.cfm

Plugs remove heat from combustion chambers...... or so says ngk.
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Offline Steve Wood

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Re: Spark Plugs?
« Reply #33 on: August 08 2018, 02:00:07 PM »
A wide gap seems to improve idle and increase plug life on longer cammed, rich idle car and reduces plug fouling.  Multi-spark ignition does the same thing.  Better burn, better emissions.

All these high voltage, plasma, or whatever ignitions seem to do nothing for hp as long as the spark is adequate to light the mixture.
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Offline earlbrown

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Re: Spark Plugs?
« Reply #34 on: August 08 2018, 02:40:35 PM »
Yep. It's a binary thing.   The plug either lights off the mixture correctly, or it doesn't.


If you're already lighting it off correctly, you can't light it off 'even more correctly' and see a HP gain.
'87 GN - 4.2L SFI Turbocharged innercooled V6 - Chrome valve covers - supra pump - 14" K&N - 52mm throttlebody - rocker shaft supports -  1/2 intake spacer - TB coolant bypass - 3" ATR exhaust tip - Alum intake pipe - NOS timing cover - chip - relocated charcoal canister - CR42's - stock

Offline Steve Wood

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Re: Spark Plugs?
« Reply #35 on: August 08 2018, 09:22:25 PM »
Looks like NGK UR-5s are the choice by far
Steve Wood

http://www.vortexbuicks-etc.com

A lot of broken parts does not make you a racer; it makes you a slow learner.


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