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Spark Plug Gap

Generation II Small Block Chevy.

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Re: Spark Plug Gap

Unread postby XtremeOracing » Wed Feb 17, 2010 2:19 pm

I just do 35 on all my motors too...
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Re: Spark Plug Gap

Unread postby 2fast4u88 » Wed Feb 17, 2010 3:54 pm

The bigger gap will make more of a hotter spark. Though with the chance to blow out. .035 gap is not needed on a all motor lt1. Heck that is what i ran on the procharged car becase of blow out.

You really want to find the best widest gap possible. All my plugs are gapped at .042 where you should be fine for the mods you have. Heck stock is .050. Where you should even be fine at that gap. The only reason I narrowed mine. Was due to ngk's seem to work better gapped to .005 smaller than factory.

Edit: Here is just a run down. I thought I would add.
narrow-gap risk: spark might be too weak/small to ignite fuel;
narrow-gap benefit: plug always fires on each cycle;
wide-gap risk: plug might not fire, or miss at high speeds;
wide-gap benefit: spark is strong for a clean burn.
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Re: Spark Plug Gap

Unread postby R3DLT1 » Wed Feb 17, 2010 6:13 pm

Good thing i have not started the tune just yet. ill leave it at .44. Thats wat my last set of NGK were.
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Re: Spark Plug Gap

Unread postby sweetbmxrider » Wed Feb 17, 2010 7:25 pm

yeah i agree with 2fast. i doubt you will see/notice any ill effects from the narrow gap but there are issues like with anything from being too much or too little.
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Re: Spark Plug Gap

Unread postby XtremeOracing » Wed Feb 17, 2010 7:58 pm

Maybe i've been running nitrous for too long... But with anything above 35 i break up badly at high RPMs when spraying...

On a stock motor tho, i would stick with 45.
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Re: Spark Plug Gap

Unread postby 2fast4u88 » Wed Feb 17, 2010 11:35 pm

The more you narrow the gap you can get worse mpg. Along with less power. You should know that extreme. I see the srt boys talk about spark plug gap all the time. Some run like .020 because they get blow out from being to rich.

Now how much gap will affect mpg and power is a different story. I would say .040 -.045 and you should be fine. Extreme you could even fix your knock. Hard to tell what was causing blow out on spray :) Just playing. That still seems to tight of a gap for spray though. Like I said I ran .035 on the procharged car with a msd coil and ignition box. Maybe you were a little bit on the rich side or something. Then again I don't know all the details for spraying either :)
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Re: Spark Plug Gap

Unread postby sweetbmxrider » Thu Feb 18, 2010 9:24 am

.035 for nitrous isn't out of the ordinary
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Re: Spark Plug Gap

Unread postby XtremeOracing » Thu Feb 18, 2010 11:10 am

sweetbmxrider wrote:.035 for nitrous isn't out of the ordinary


Yea when i did anything above .035 and sprayed, as soon as i hit 5000RPM it felt like i was riding a horse.
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Re: Spark Plug Gap

Unread postby shownomercy » Thu Feb 18, 2010 11:22 am

XtremeOracing wrote:
sweetbmxrider wrote:.035 for nitrous isn't out of the ordinary


Yea when i did anything above .035 and sprayed, as soon as i hit 5000RPM it felt like i was riding a horse.



See, you guys are treating spark gap as if its the only variant here. Anything past stock CR, or HP levels will call for differing heat ranges in spark plugs, and you cannot adjust for that via spark gap.

Now, for stock engine etc, sure debate gap, but you cannot compare a modded motor to a stocker.

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Re: Spark Plug Gap

Unread postby sweetbmxrider » Thu Feb 18, 2010 12:33 pm

very true but you still want to lessen the gap on the proper plug per application

Insufficient spark plug gap can cause pre-ignition, detonation, even engine damage. Too much gap can result in a higher rate of misfires, noticeable loss of power, plug fouling, and poor economy.

When you raise compression or add forced induction (a turbo system, nitrous, or supercharger kit), you must lower the gap (reduce gap about .004" for every 50 hp you add on an V-8 engine). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology,) you can open the gap back up about .002"-.005".

As an example, let's use a hypothetical `96 350 Chevrolet LT1 engine build-up. The standard gap is .050" for an un-modified LT1. We'll add 150hp Nitrous, so we must lower the gap about .012" to .038". We then decide to add that killer MSD 6A/Crane Hi-6 box and, using our guidelines as outlined above, we can now open the gap up .002"-.005" to about .040"- .043". By following this basic guideline should get you very close.

Further experimentation may be necessary, but by always starting with a larger gap than it thought necessary to reduce the risk of detonation, you should be safe.


Spark Plugs and Nitrous Oxide:
What Works, What Doesn’t, and Why
Over the years there seems to have been a great amount of technical material written about the simple operation of a spark plug and what they can do in relation to the way an engine runs. There are a few basic characteristics about spark plugs that you need to know to make an intelligent choice about the correct spark plug for your application.
First, and most important; a spark plug must be of the correct design to operate within the environment of your engine not the other way around. This means that the spark plug has virtually no influence on how the engine burns fuel or runs in general. The correct spark plug will simply survive the conditions present in your engine. A spark plug must maintain a certain temperature to keep itself clean. The wrong heat range can cause an overheated plug or a fouled plug. The heat range refers to the temperature 0f the ceramic material surrounding the center electrode.
Lean air/fuel ratios are more difficult to light because there are less fuel molecules in the area of the plug gap when the plug is scheduled to fire; thus, protected nose plugs were designed for late-model lean-burn engines. Modern high-energy ignition also allowed larger plug gaps. All the while this was happening, something else happened. Something that no one seems to have really noticed as the real culprit when the issue of factory type plugs being used with nitrous comes up. We’d like to clue you in.
Quite often, a factory type, wide-gap projected plug will produce a misfire condition after only a few seconds of nitrous use. The misfire is not due to the heat range. The misfire occurs because the ground strap of the spark plug becomes a glowing ember because it is too long to dissipate the extra heat produced by a nitrous-accelerated burn condition. The correct fix for this phenomenon is to replace the plugs with one that has a shorter ground strap. By doing this, you will shorten the path for the heat being absorbed by the ground strap. You can use the same heat range, you just have to find a non-protected nose plus with a shorter and preferably thicker ground strop.
If you only change the heat range of the spark plug to a colder heat range, you may very well still have the misfire problem. Since the length 0f the ground strap is the cause the misFire, a colder spark plug may have the same length of ground strap as the hotter plug you replaced it with.
Spark plug gaps should generally be .030” to .035”. Never try to gap a plug designed for an .060” gap down to .035’. Find the correct non-projected nose plug designed for an .035” gap.


http://www.nitroussupply.com/tuning.php

just sayin....
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