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Spark Plug Info.


jcrome04
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Ok I have been confused with this many a time and think this might help clear up some confusion with others as well.

So I have a 97 LS400 with the 1UZFE (obviously) :rolleyes:

The spark plugs are recommended to be gapped at .044 and platinum.

NGK plugs I have purchased in the past (iridium AND platinum) say "DO NOT GAP" being that the fine center electrode may break.

A gentleman at my local Schucks Auto said they needed to be gapped. <_<

I would trust the box over the employee but I've heard to gap them from multiple sources and just want to 100% know the right answer!!!!

Is there really a big difference between the IX Iridiums and the GP Platinums other than price?? (platinums are about $20 cheaper than the Iridiums)

Ps. I have not gapped ANY of them I have purchased!

Thanks Everyone!!!

Keep a look out for my "how-to" of Seafoam AND Fog light re-wire mod (95-97 LS400), both with detailed photos!

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Ok I have been confused with this many a time and think this might help clear up some confusion with others as well.

So I have a 97 LS400 with the 1UZFE (obviously) :rolleyes:

The spark plugs are recommended to be gapped at .044

NGK plugs I have purchased in the past (iridium AND platinum) say "DO NOT GAP" being that the fine center electrode may break.

A gentleman at my local Schucks Auto said they needed to be gapped. <_<

I would trust the box over the employee but I've heard to gap them from multiple sources and just want to 100% know the right answer!!!!

Ps. I have not gapped ANY of them I have purchased!

Thanks Everyone!!!

Keep a look out for my "how-to" of Seafoam AND Fog light re-wire mod (95-97 LS400), both with detailed photos!

OEM plugs do not need to be gapped.:cheers:

You can check them so you can sleep @ night...................

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I would gap them. And use Denso's, they are a much better plug than the NGK's. It's the same spec gap for the IS 300 as well. Remember, it's not just about the spark. It's about the flame kernel. The smaller the gap, the smaller the flame kernal it produces. The smaller the flame kernel, the less efficient or I should say the less ability to burn all the air fuel mix in the chamber. Which in most cases just means a little more work for the cats, but still a waste. The only time you should go with a smaller gap is if you increase compression with say a turbo, or supercharger. In that case what happens is the air rushing into the chamber blows out the spark and causes fouling and misfires. But if your running stock, then I would gap them. The NGK's you are running fit any number of cars.And they all have slightly different gap requirements. There is no way they can make one plug to accomidate every application. And by the way, the size of the center electrode has nothing to with the ability to gap them or not. The electrode they refer to is the grounding electrode, the metel L looking piece that you would bend to open or close the gap. Which let me touch on here. We are talking about bending an electrode approx. .020!!! From the out of the box .024(ish) to .044 for spec gapping. Come on, your afraid it's gonna break off cause you moved it that little bit? In all my years of motor swaps, retunes and change outs between races, I think we only ever cracked insulators as the big issue. We never had a ground electrode issue.

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I've always gapped my iridium plugs becuase the Lexus repair manual says that new plugs should be gapped to 0.8mm in the '95 LS. I just recently bought a set of 8 NGK Iridium IX plugs for $50 shipped on ebay!

My bad :blushing: I meant check the gaps, They are usually spot on............

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the difference betweeen the platinums and the iridiums is the ability to stand up to wear and tranfer heat from the tip of the plug. The smaller the electrode, the less heat it can hold and the easier to tranfer away from the tip and keep it from melting.

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I thought it was talking about snapping off the tiny little point in the middle, because it says "fine center electrode"

So they should be gapped to .044?? Thats what I am being told the gap is online

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Modern spark plugs are very accurately manufactured. In many cases the part numbers include a designation for gap, meaning that they are gapped during manufacturing. The small electrode can be damaged by checking, and there is no need to do so. The shape of the center electrode is critical to the formation of the spark, and that is far more important than the gap itself, given that all modern engines use electronic ignition systems capable of firing almost any gap.

If the manufacturer states "Do not gap" why would you second guess them? Because some high school drop-out living in a trailer says so?

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Modern spark plugs are very accurately manufactured. In many cases the part numbers include a designation for gap, meaning that they are gapped during manufacturing. The small electrode can be damaged by checking, and there is no need to do so. The shape of the center electrode is critical to the formation of the spark, and that is far more important than the gap itself, given that all modern engines use electronic ignition systems capable of firing almost any gap.

If the manufacturer states "Do not gap" why would you second guess them? Because some high school drop-out living in a trailer says so?

:cheers: Bingo

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I just threw my ngk iridium's in 2 weeks ago and love them.

They came "pre gapped" with cardboard ends to make sure they did not change while in the packaging.

I don't bother checking the gap any more as they are always dead on.

Platinum last longer but is not as efficient in spark, copper used to be the best for the electrode for low resistance and did not last as long. but iridium takes higher heat levels and is less resistance.

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So when you take it to the dealership and they change plugs, do they gap them to mfgr. spec, or listen to what the writing on the box says?

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I've never heard about a dealer putting in NGK Iridium IX but I'm sure if they did, they would listen to the manufacturer Specs. Which for NGK Iridium IX (and also NGK GP Platinum) would be to not touch the gap.

This thread is done, all I wanted was some info, I got it. There no need for everyone to start arguing now over gapping plugs.

Thank you everyone for all your help and information. It is GREATLY appreciated. :cheers:

As for this topic.... I pray it's done :closedeyes:

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If the manufacturer states "Do not gap" why would you second guess them? Because some high school drop-out living in a trailer says so?

Hey, he said it was a "gentlemen" at Schucks. Gentlemen dont lie, do they? :whistles:

As far as he plugs go, trust but verify. Just do a visual sanity check on the whole lot. If they look consistently gapped, put em in.

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but what if they're not gapped enough. I didn't stick the gapper in but they weren't anywhere near .044 ...what then!!! they are supposed to be "pre-gapped" but they aren't anywhere near the recommendation of .044

they were around .03-.035 or so...

Should I still trust the plugs if they aren't gapped enough??

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I like what Landar said:

As far as he plugs go, trust but verify.

All parts are manufactured to specified tolerances. Meaning they are not exactly the same. Each manufacturer has their own parameters. Within those parameters you will have batches that vary in their specs. If as SK has done, you find a brand that is consistent enough to gain your trust, makes life simple. I would still do a spot check from time to time.

Smooth1 asks:

So when you take it to the dealership and they change plugs, do they gap them to mfgr. spec, or listen to what the writing on the box says?
My guess is that a Lexus tech would be installing plugs that have been pre-gapped. I don't think the dealership would want them spending their time gapping plugs.
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but what if they're not gapped enough. I didn't stick the gapper in but they weren't anywhere near .044 ...what then!!! they are supposed to be "pre-gapped" but they aren't anywhere near the recommendation of .044

they were around .03-.035 or so...

Should I still trust the plugs if they aren't gapped enough??

There is no way you should have to change a plug gap more than a few thousandths - any more than that and you have the wrong plugs. The geometry of the ground electrode to the center electrode is critical - like I said before more important than the gap even - so bending the crap out of the side electrode is not something one should have to do to plugs that cost that much. Bosch states the gap on the box, and I have seen some NGK's do the same.

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Smooth1 asks:
So when you take it to the dealership and they change plugs, do they gap them to mfgr. spec, or listen to what the writing on the box says?
My guess is that a Lexus tech would be installing plugs that have been pre-gapped. I don't think the dealership would want them spending their time gapping plugs.

I'm not out to sell the idea of gapping or not. To each thier own. But to clear up this point, Lexus of Orlando and I get our plugs from the exact same distributor. Because I want Denso's. They come out of the box .026 -.028 gaps. The mfgr spec gap is Denso (SK16R-P11) and the gap is .043 or 1.1 mm. And yes, they gap them to spec. at the dealership.

To small a gap may be why some of you have 02 sensor issues later, or some other problems. It's kind of like eating bacon, does it cause heart desease??? NOOoooo, but it doesn't help prevent it in anyway, and it could be linked to helping cause the issues later. But then you have some people who eat a pound of bacon a week, and live to be a hundred.

So, if your not gapping them , then don't. Simple. And if your doing it yourself, then you should be inspecting the plugs as they come out and you would know what a lean condition plug, vs. a rich condition and what a good plug would look like. So you can address the issue then. The rest of you that pay someone else to change the plugs for you? Well, you'll just have to either check it yourself, which would negate the convienience of having someone else do it for you, or just trust that the person under your hood knows what is best and performs to those standards.

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