irridium spark plugs (Page 1/3)
sledcaddie FEB 19, 04:27 PM
Because of the slight difficulty in changing spark plugs on the 2.8 V6 (front side), I've considered using irridium spark plugs, due to their long lasting durability. I had used them on my previous Fiero without any issues. What is everyone else's opinion/experience with irridium spark plugs? Thanks for all who offer input.
Vintage-Nut FEB 19, 05:07 PM
Brand Matters - Use ACDelco

Many members 'swear' that the Original Equipment R42TS Copper plugs are the best on the V6, but like you - I 'hate' changing the right bank plugs so often......

I changed to ACDelco Platinum "Rapidfire" Spark Plugs many moons ago for the same reason and never looked back!

*EDIT*
After reading comments below, I hope PFF members know that the factory 30k-volt ignition coil is the 'weak link'.......
And of course, everybody has different priorities on a spark plug.........Performance, Maintenance and Cost.
Mine: Normal Street Use and Low Maintenance / 50k-Volt Coil and Platinum Plugs @ .045 Gap

------------------
Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

[This message has been edited by Vintage-Nut (edited 02-20-2024).]

1985 Fiero GT FEB 19, 05:43 PM
Copper are technically better, and using other types can lead to some weird behavior in some cases, behavior that is hard to troubleshoot, as many ignition issues are, can cause slightly less power and fuel efficiency, perhaps replace your dogbone bushings, that will pull the engine back up to another 1/2 inch, which can definitely help with access.
Another thing to think about is that you might want to change them more regularly, as the front bank has the tenancy to rust in, which is much more of a pain to get out then 2 or 3 normal changes, with no rust, it is honestly equivalent to changing the oil filter, which has to be done very frequently. Just get in the trunk, lay on the intake, and find the right combination of extensions to get them out.
cvxjet FEB 19, 06:13 PM
I installed the ACDelco RapidFire plugs in my 3.4 F-body converted V6....One thing that made the front three much easier to change; jacked car up, then removed the dog-bone and the two rear subframe bolts and using my jack lowered the engine/trany/subframe a few inches which tilted the engine back...

Just make sure you reinstall the bolts and dog-bone (had to chase my dog around the yard to get it back from her)

Also, I used compressed air to blow out debris from around the plugs, then sprayed some penetrating oil around the base of the plugs and let it sit for a day- then started the engine and let it run for a few minutes (Applying some heat)...then, after cool-down, sprayed some more...a couple of days later, the plugs came out easy.

[This message has been edited by cvxjet (edited 02-19-2024).]

OldGuyinaGT FEB 19, 06:39 PM
Opinions about spark plugs, especially in Fieros, vary about as widely as opinions on where you can get the best cheeseburger. At any rate, here's my experience regarding spark plugs and my one essentially stock 1988 Fiero GT.

I use NGK Iridium IX in all my cars for the past decade or more - except my Fiero).

Several years ago I put IRIDIUM plugs in the Fiero and it seemed not to like them much. So I put stock Champions in it and did a lot of troubleshooting of the ignition system and finally got it to run really well. By the way, NONE of the problems were the plugs, but then, I already had the garden variety Champion Copper Plus plugs in it when I got it sorted out, so I left them.

BUT...

In my experience, most 'standard' spark plugs degrade fairly quickly compared to the more exotic ones. My rule-of-thumb over the last 50 years or so has been that they should be replaced every 15-20,000 miles, regardless of engine or make or ignition system. I did feel like the ones in my Fiero were showing some age and wear before 20k. I was a little hesitant about going back to iridium, because my ignition system is completely stock (unless you want to make an exception for my 'star-wheel' type distributor) - stock coil, stock ICM, spiral-wire core plug wires. I read a white paper (got it here somewhere).where I read that iridium and some other electrode materials were harder to fire than metals like nickel or platinum (most all plugs have copper cores). In the end, I went with NGK G-Power Platinum plugs. They don't have the expected life of iridium, but way longer than standard plugs. They're running great, after two years and about 7000 miles. They say platinum plugs will last " up to 100,000 miles"; I'll be looking to replace these at maybe half that.

None of this is to say that iridium plugs won't run well in a stock Fiero; just my experience, and I haven't tried iridium plugs in my Fiero since that troubleshooting stage. But I sure like these platinum ones right now.
82-T/A [At Work] FEB 19, 07:32 PM
I have no opinions on this... but I'm curious to learn more about why certain plugs are recommended for certain engines.

Anyone know a good website that explains the heat rating, depth, etc... of the spark plug? And finally... the difference between the metals and why it matters? I know that some metals are more conductive, but that some of them also corrode faster (like Copper or steel). Some require a hotter voltage to produce the same spark for a more conductive metal with a lower spark, but don't last as long.

Is there a good chart for this?
1985 Fiero GT FEB 19, 08:40 PM

quote
Originally posted by 82-T/A [At Work]:

I have no opinions on this... but I'm curious to learn more about why certain plugs are recommended for certain engines.

Anyone know a good website that explains the heat rating, depth, etc... of the spark plug? And finally... the difference between the metals and why it matters? I know that some metals are more conductive, but that some of them also corrode faster (like Copper or steel). Some require a hotter voltage to produce the same spark for a more conductive metal with a lower spark, but don't last as long.

Is there a good chart for this?



This has some good information: https://www.fierofocus.com/.../art-sparkplugs.html

I think it is mainly the conductivity, the factory v6 ignition system is underpowered to say the least, they use the same coil as the 4 cyl, to run 50% more cylinders, which means it is underpowered, especially at higher rpms. With stock .045 gap, copper plugs will have the best conductivity, and the hottest best spark, other plugs may not have a good disk with the stock coil, but with a better coil, that will make up for the lower conductivity, and give you normal spark with the long life. If you upgrade the coil, and keep the copper plugs, and increase the gap so you have a normal spark intensity, but it is bigger due to the better coil, you can get actual power gains.

Bottom line, more power=some combo of copper plugs, better coil, bigger gap. More life with original power=other plugs, better coil, original gap. What most people do=other plugs, weak coil, same gap=less power, less fuel economy, etc.

All of this is dependant on rpm to, if you never go above 4000, you might not notice any difference in plugs, or gaps, or whatnot, but apparently power drops off majorly around 5000rpm because of the load on the coil.

[This message has been edited by 1985 Fiero GT (edited 02-19-2024).]

Spadesluck FEB 19, 09:42 PM

quote
Originally posted by 82-T/A [At Work]:

I have no opinions on this... but I'm curious to learn more about why certain plugs are recommended for certain engines.

Anyone know a good website that explains the heat rating, depth, etc... of the spark plug? And finally... the difference between the metals and why it matters? I know that some metals are more conductive, but that some of them also corrode faster (like Copper or steel). Some require a hotter voltage to produce the same spark for a more conductive metal with a lower spark, but don't last as long.

Is there a good chart for this?



Plugs for Forced Induction are important because of the heat range. You typically go with a colder plug because of the compressed air being forced into the cylinder. Beyond that I just look at a spark plug as a spark plug, don't get lost on the snake oil of the "fancy" plugs.
sledcaddie FEB 19, 10:28 PM
In doing some more research on this, I found an interesting article. It compares the pros and cons of irridium to platinum. https://rxmechanic.com/iridium-vs-platinum/ The main thing I took from this article is that all plugs have a copper-core element. It is just the tips that are made of different materials. Irridium costs double that of platinum. The higher cost of the irridium plug was the only 'con'. The main benefit is that the irridium tip lasts twice as long as the platinum tip. Hope this info helps others.
82-T/A [At Work] FEB 20, 08:19 AM

quote
Originally posted by 1985 Fiero GT:
All of this is dependant on rpm to, if you never go above 4000, you might not notice any difference in plugs, or gaps, or whatnot, but apparently power drops off majorly around 5000rpm because of the load on the coil.





I can absolutely attest to this. Back over 15+ years ago when I used to drive my 87 SE/V6 regularly... it performed just as you said until I upgraded my ignition coil. I went with an Accel SuperCoil (or whatever it was called back then). Bright-yellow coil which I spray painted black to look stock. I noticed idle was slightly improved, but that could have just been plecebo. I didn't notice any power increase until around 4,500+ rpms. Essentially, the difference was that the engine continued to pull strong as it did in the mid-range, and it felt like I had more actually usable power in the upper RPMs than I did before. It clearly made a difference.

I've had a lot of people tell me this isn't so... maybe my stock coil was starting to go... but either way, your point about the 4cyl coil and the V6 coil is on point. The coil is basically a capacitor of sorts... and it simply cannot maintain / recharge quickly enough to provide that level of voltage to the spark plugs at the higher RPMs. There have actually been dyno tests that have shown this. I saved them somewhere, so maybe I'll make a page about it one day.


For both my daughter's car, and my car, we plan to use the MSD 6EFI system. In addition to the multiple spark discharge feature, it also provides a more complete burn to help eliminate carbon deposits from ever occurring... or at least not as frequently, and is supposed to smooth out idle. On her little 4 cyl, I doubt she'll ever see a power increase from it, but anything we can do to improve the efficiency of the motor will be useful. For me, it's about the learning opportunity with her. We'll rebuild and put everything back to stock, and then install that in an inconspicuous place along with the factory wiring to see if there's a change in idle and normal around-town driving.