NGK spark plug

[Cutlass]

So I'm replacing my spark plugs during my LT and ORY install and I pulled out the spark plugs. They are NGK platnum plugs with a GM part number on them. Are they the original factory plugs??
I'm pretty sure I'm just gonna install new AcDelco or NGK iridium plugs back in but I've been reading spark plug threads for hours and EVERYONE loves the NGK Tr55s but no one says why they are so much better. I have stock heads and cam so either plug should be just fine, but can someone convince me why I should install the TR55s instead of Iridium?

[shady milkman]

So I'm replacing my spark plugs during my LT and ORY install and I pulled out the spark plugs. They are NGK platnum plugs with a GM part number on them. Are they the original factory plugs??
I'm pretty sure I'm just gonna install new AcDelco or NGK iridium plugs back in but I've been reading spark plug threads for hours and EVERYONE loves the NGK Tr55s but no one says why they are so much better. I have stock heads and cam so either plug should be just fine, but can someone convince me why I should install the TR55s instead of Iridium?

i believe denso and some ac-delcos where the stock ones. I have the tr55s and i will more than likely soon swap them out for some iridium plugs...coppers have too short of a lifespan for my DD and so forth..i cant say why people think they are the shit.

[pajeff02]

As it was explained to me -- the Iridiums are quite expensive and none of us "car guys" are going to run plugs for 100,000 miles anyway, so why spend the extra money. Everyone appears to have good luck with the TR-55's, so I did install them on our car.

[Hi-Po]

I thought the stockers were,

ACDelco 12
ACDelco 41-985

[thearborbarber]

The factory plugs that I took out were NGK with a delco part number as well.

[Cutlass]

Ok so I've read the following info on some random website and it seems to make some sense.

Copper core plug advantage: stronger spark because it requires more voltage than platinum- or iridium-tipped plugs if all are at the same gap. This theoretically means better chances for combustion and so better power.

Copper core plug disadvantage: stronger spark because it requires more voltage than platinum- or iridium-tipped plugs if all are at the same gap. This means the ignition wires, coils, and power transistor must produce more energy to fire copper core plugs at say 0.036" gap than platinum- or iridium-tipped plugs at the same gap. This can mean more misfires at higher cylinder pressures and/or higher engine rpm at larger spark gaps.

Copper core plug disadvantage: electrodes will wear 2 to 6 times as fast as platinum- or iridium-tipped plugs and so must be changed more often.

[Cutlass]

Also found this which seems a little confusing:

Improved Firing Performance :
To improve firing performance, the contact area between the electrode and the flame nucleus needs to be reduced in size. This is why the iridium electrode was made as fine as possible to a diameter of 0.4mm. Compared to normal Spark Plugs, with a spark plug of 0.8mm, the ignitability limits are better by 2.5. Less metal on the tip allows the spark to expand in a greater area, maximizing firing performance and minimizing voltage requirements.
The required voltage in the Iridium plugs is between 3000 volts & 5000 volts that is less than a normal plug. This is due to the ultra-fine 0.4mm diameter ground electrode. Because the required voltage is kept low, Iridium plugs can be used in high performance engines and for high response driving. Smoother Idling: When an engine is idling, firing can become particularly bad. Because Iridium Power plugs have a low required voltage and high ignitability, sparking continues to work properly during idling. Whereas normal plugs have highly variable rpm counts, Iridium Power plugs maintain very smooth idling. Also, because combustion is good, the explosive energy raises the rpm count.
Improved Engine Performance :
Iridium Power spark plugs enhance the performance of an engine. Acceleration is improved when compared against normal spark plugs.
Decreased Fuel Consumption:
When Iridium Power spark plugs are used, accidental fire and misfiring rarely occurs under various driving conditions. Therefore, combustion is extremely good. In turn, a healthy engine can be maintained and fuel consumption improved. So why not use an Iridium plug?

[pajeff02]

I don't think there is any question that the Iridium plug is a "better spark plug". I guess it comes down to a matter of what you want to run -- just like oil, air filters, or whatever. Should our car start throwing misfire codes with the NGK's or exhibit ignition performance issues then I would probably switch to Iridiums.

I agree, the first article makes sense... the second is a little more confusing and sounds like advertising.

[marksls1ta]

The TR55s is what we recommend for the the NA cars.

Thanks,
Mark

[Cutlass]

Ok so I might be a tad obsessed with spark plugs at the moment, but I finally found an answer to my question on a truck forum. This is a great explanation and might even be Sticky worthy. Here's the quote:

I have been using NGK V-Power TR55 plugs for 5 years in my GM V8s I've owned... I posted quite a large post in this thread, and rightly so, I am VERY fond of the TR55 version... I currently have them installed on the AV, and have run them for about 70,000 miles on New Vortecs, LS-1s, and LT-1s ...

I think Platinums have their place, as well as the standard plugs do their's... This is a very complicated topic, and I will try not to get out of hand this time...

The first thing you must determine is the goal of the plug change, and apply what you read here to your goal, and be honest with yourself... What I mean is, justify the need before you change...

Before I go into details, plugs are as big a mystery as anything can be in the sense of the word... The debate will rage on about handgun cartridges as in what's better for protection: 9mm para, or .45 Auto? Or .45 Auto or .357 Mag? The debate will go on forever... As it is with plugs: What's better Platinum or Standard? I will mention facts, and you decide for yourselves....

The NGK TR55 here will serve as the "Standard" plug, and the NGK TR55GP will serve as the "Platinum" version which in fact for you gear heads, the TR55GP is the current replacement to the TR55VX in the 5.3/4.8/6.0 ...

The job of a spark plug is mainly 2 things... 1. To ignite the air/fuel mix at the proper time, and 2. To help conduct heat away from the upper part of the combustion chamber (Head) ...

The plat, and std NGK do fine for carrying heat away from the head via through the plug to head to water jacket... The construction of the plug internally is pretty much identical... They both have a pure Copper core, triple laminated gas seal at base, and an Alumina Silicate Insulator... That covers the internal construction comparison... So now we are left with the actual electrodes where the business is at!

Standard plugs with a hardened steel center electrode, and ground electrode will require more voltage to get the spark to jump the air gap period... A Platinum plug requires much less to accomplish the same because the center electrode is MUCH thinner, and it's just plain physics that it takes less voltage to jump a gap between two needles vs. jumping across 2 solid pipes... Hold onto the needle in flame, and the solid pipe in the same flame... The tip of the needle will glow red hot while the pipe will also, but will take much longer...
For simple terms, the Plat. tip will glow way before the steel tip will... This will come into play if your current set-up is sensitive as far as detonation goes... You will have less chance detonating using a std. plug vs. a Plat. By the time the piston makes it's second trip back up, that Plat. tip because it's very thin, may not cool enough and will cause the air/fuel mix to pre-ignite or detonate... This will probably occur at high rps where the cycle time of the plug is very fast... Now, there are other things that can cause detonation like too lean of A/F ratio, too much timing advance, hot ambient temps, hot head temp, low octane fuel, etc... So, if you hear the motor pinging, don't jump to the plats. being the cause, I'm just mentioning a possibility with Plats. vs. Std...

Now that we know the tip on a Plat heats quicker, and a steel std heats slower, we can be safe saying a plat is not a good plug for NOS OR Forced Induction...

The tip on a Plat. can be thinner because it's Platinum right? And Platinum on a plug will melt at about 2000-2100 Degrees Kelvin ... The steel will melt at about 1600-1800, (and Iridium at about 2500+) The Plat tip is thinner because of alot of reasons... It increases the effeciency and reliability of the ign system because it requires MUCH less voltage to fire, it keeps it's performance longer due to the harder plat's tips reducing erosion at the tip, and one thing I just learned, it centers the spark in the air gap EVERYTIME to allow an evenly ingnited air/fuel mixture ... The flame front starts in the center of the combustion chamber EVERYTIME on a plat plug insuring a consistent power curve in the cylinder EVERYTIME... On a std plug with a fat center electrode, it might happen on the right side, left side, bottom, top, etc... This will cause the explosion to be non-linear, and uneven... This phenomena can cause piston rock, and with the short ring lands on our pistons vs. the piston slap noted on some new gen V8's, may not be a wanted event... The NGK V-Groove plug has a V cut in the center of the center electrode, which DOES force the spark to the outer edge of the electrode, but it cannot guarantee which side of the V it will be! ... All it rules out is that the spark will not occur in a shrouded area directly under the ground electrode... Let's say you have a TR55 in cylinder # 6, and it fires primarily on the left side of the ground electrode for 30,000 miles... That cylinder has seen slightly "unbalanced" combustion cycles for that long... This I think, why people notice a smoother idle and smoother rev cycle when going to plats.. The fine electrode centers the spark, and has the same degree of shrouding all the time.

Now you say, but I thought the TR55s were better? Or if they make more power, they Must be better... Well, in many ways they DO have advantages over a Plat... Forced induction for one! The priority is reliability, through intensity... The std. plug does have more spark intensity period... It has more surface area on the electrode which allows a fatter spark... This is why some notice better throttle response when going from plats to std plugs... The std plug simply gets the fire propagated quicker... But, again at the expense of higher voltage requirement...

So, to conclude...

Plat. benefits:
------------------
- Last twice as long (60,000 max)
- Reliable under low voltage conditions (less misfires)
- More consistent spark path
- Creates centered flame front to reduce piston rock
- Gap erosion is less as long as Plat plating is intact... This allows more consistent gap through life of plug...

Plat. Drawbacks:
---------------------
- Retains heat longer at center electrode increasing possibility of detonation
- Has less spark INTENSITY
- Because of less intensity, not good for Forced induction
- More expensive


Standard Benefits:
-----------------------
- More Spark intensity gets it on in the hole faster
- Center electrode being thicker disperses heat better(reducing possibilities of detonation)
- Less expensive
- Better throttle response


Standard Drawbacks:
---------------------------
- Lasts half as long as platinum (30,000 max)
- Spark "focus" is erratic possibly causing piston rock due to un-even flame front
- Requires more voltage (although NGK V-Groove plugs reduce this because of the smaller surface area on the center electrode)
- Center electrode erodes faster, and consistency is ever changing through the life of the plug...

[Cutlass]

And continued:

So now you say, thanks 11H for adding to my confusion!!!!

Here's what I would recommend:

Platinums for the broad bunch of folks unless you want that last ounce of power, throttle response, or run NOS or blowers... If you have a detonation issue, I would not try to solve it with going to std plugs... It's probably something else causing it... I have seen TR55s make 4 hp on the dyno over the older AC plats, but since 2000, GM has been using a very good DENSO Double Platinum in the trucks... I think the older AC single plats were junk...

The factory gap on NGK TR55's is: .0050
The factory gap on TR5's is: .0039
The gap on a std plug should be decreased by between 9 and 13 thousandths below GM's recommended gap due to the increased voltage requirement...
The plats. can run more gap to allow more spark length, because they have a much lower volt requirement...
The plats. need big gaps to give good un-shrouded spark...
As far as the ignition systems on our trucks, I think they will support just about any plug or gap you run as long as it does not exceed .0060 ... The new ignitions are a big improvement over year's passed ... Remember though, if the electrical system is running poorly or low on voltage, and those NGK std's have been in there for 30,000 miles, it may be a good chance of seeing a mis-fire...

To mention Iridium plugs... I'm sure some will wonder about them...

In short, they are a really great concept... BUT the way they are currently designed, they make the tip of the center electrode thinner than a plat plug by about 25% ... They DO have a higher heat durability factor (about 300 degrees Kelvin) over the plat., but they bring it's virtue down to a plat's level due to the decreased tip diameter... In my opinion, the life will be the same as a plat., and it will require even LESS voltage than a plat, but what it will do is not dissipate heat as fast as a fatter tip will due to it's reduced surface area... This will increase the chances of detonation over a plat. plug... Personally, the only benefit I see is reduced voltage... But disadvantages may be increased possibility of detonation, and extremely high cost... We don't need the lower volt benefit of the things in our ign system...

I have made an observation, and the new NGK G Power plug looks to mimic the fine electrode of the Iridium design... The NGK cross reference for our trucks used to be TR55VX for platinums... The new part number is TR55GP for G Power... I ordered a set of these from clubplug for $3.41 each ... The NGK Iridiums are TR55IX, and were $6.67 each...

In our world at least, the Irids are useless... My opinion of course... The denso irids are like $13-15 each haha...

Here's a link that shows the possible combinations of plugs for the 5.3 (it's the LS-1 board, but they run the same plugs):

http://www.ls1info.com/article.php?sid=45

*** For every added 75 HP over stock, you should go to one stage cooler plug... The plug body actually runs HOTTER and carries more heat from the combustion chamber to allow the combustion chamber temps to be lower... These "cooler" plugs give up alot of life to add this benefit... Running a cooler plug in a NA motor will foul quicker due to the plug's inability to reach the electrode's self clean temps...

[pajeff02]

+1 Great information and answers all the questions.

[Smittro]

After reading this post alot was explained.. I run the delco Iridiums. I removed the old Iridiums recently when I was having (@ the time) unknown misfire issues and replaced them with a new set. Appearantly delco has changed the iridium plug (@ least for the v6ers) the old plugs had a pointed electrode on both sides (top and bottom). However the new Delco Iridiums I installed only had the pointed electrode on the "emitter" side and the ground electrode no longer has a pointed electrode, but rather a flat one with a tiny flat disk on it. I had no real clue as to why they were changed.. But after reading this post I think I have an idea.. Maybe something to think about and or look into.. just my .02... For the record I run delco Iridiums in everything vehicle wise. Everything else (lawnmowers,tractors, ect) I run NGK's..

[Smittro]

Oh and to add.. I found that when I had my z34 emissions tested, the Iridiums seemed to cause it to pass 15% below state minimum requirements even with the cams set -6 exh.and +6 int.. The standard Delco plug for the engine was notably higher but still passed.. My z34 had become exempt from emissions testing right before I pulled her off the road for the TT project and will remain so after she retakes the road. I will still run Delco Iridiums unless I see detonation (knock) displayed on the engine monitor screen for the stand alone where I can easily control timing and AFR's/boost..