Good morning, nice thunderstorm here,

It has been asked before so forgive me but with offshore quality changing constantly I would like to ask again. 1987 stock L98 HEI, I have been head down in my engine for 30 days and am just about to stick the plugs back in, are iridiums that much better? My current AC5 plugs have about 2000 miles on them. I am trying not to torture the plug threads again for as long as possible, (I use a small amount of antiseize).

Thanks for your input.
.

 

I've tuned hundreds of vehicles over 25 years and developed a method which works if you can follow it exactly to preserve plugs for 100k miles

Yes use iridiums, but, caveats
1. You must never touch the plugs anywhere with bare hands, only use clean new disposable gloves and replace gloves if they get smudged or touch something like oil or antiseize
2. Apply only a tiny tiny dab of antiseize near the upper end of the plug, away from the tips where the spark is.
In your picture it looks like too much anti seize applied too close to the business end of the plug and it oozes down over time and obfuscates the conditon
3. Do not gap the iridium plugs unless you have a soft tool which does not indent the metal materials of the plug, a microscopic change due to a pliers or similar is not good for long term plug condition and the smallest microfracture in the materials disrupts conduction and field
4. Do not install new plugs unless the engine is already fully tuned. Do not tune an engine using iridium plugs, they collect evidence of poor tuning and cannot be cleaned. Always tune engine using cheap copper plugs first then switch to iridium.
5. Do not install iridium plugs unless the engine is producing clean plugs in every cylinder (fully tuned AND clean combustion chambers)
6. The engine is ideally tuned to 14.9 to 15.2:1 air fuel ratio to maintain clean appearance of spark plugs. Tradition a/f of 14.7:1 will gradually brown and discolor the plugs over time.
7. I recommend index the plugs if you intent to leave them for 50k - 100k miles

In your picture the appearance is grainy with sand-like could be anti-seize, make this this is not happening to new plugs before you use the expensive iridiums

 

Thanks KingtalOn,
These have been out a while on the desk while I have cleaned several times with the blower. I have just installed a bunch of new stuff so I will hold off on iridiums until I have a well running L98. Thank you very much for the help, I would have surely destroyed them.
Donny

 

NGK Laser Iridium...no exceptions.

 

I successfully use iridium NGK in Nissan/Toyota/Chevrolet applications up to approx 800-1300bhp using stock engine internal components for 50k miles or more.
They are up to the challenge, if you can keep them clean and fully tune the engine before they go in.

The key to a clean combustion chamber is PCV and air filtration. Maintain a factory PCV system setup and appropriate air filter pressure drop of approx 0.5" to 1.5" Hg at the throttle valve like OEM engines provide for WOT crankcase scavenging. Do not use catch cans or large lines which induce pressure drop due to friction and disorganization due to mass flow energy requirements, PCV energy is limited in wet sump applications that do not have vacuum or dry sump pumping.
This in turn will keep oil from creeping into the ring packs over time which will keep the chambers clear from oil and keep the rings clean spinning freely. Low crankcase pressure also prevents oil seals from leaking and will reduce large oil droplet formation and help oil return to the oil pan which further prevent aspiration and oil consumption over time. Low crankcase pressure also will reduce blowby by preventing early ring switching, at the end of power stroke crankcase pressure is balanced by inertial forces of the piston ring and a high crankcase pressure causes excess blow-by by forcing the ring out of position early in the power stroke allowing oil to invade the rings and may also induce ring flutter which carries more oil into the rings and allows more blow-by.
Crankcase pressure is an overlooked and essential aspect of performance engine cleanliness right up there with proper air filtration.

This is how you can achieve a clean set of plugs after significant miles stack up, along with regular oil changes will keep rings clean and spinning freely thanks to clean air (air filtration from quality filters such as PAPER OEM filters) and PCV system.

My method is first to tune the engine on cheap copper plugs,
Then install a new set of copper plugs and put 2k to 5k miles on them to ensure they stay clean,
then finally the perfect final set of iridiums goes in super clean and NEVER REMOVE THEM from that point on. Do not disturb them.

 

Iridium = junk , gimmick plugs like splitfires.

they easily foul up , if an o2 sensor goes bad
leaving you with a no start condition as they did me

they are more susceptible to fouling due to smaller electrode area (iridium is expensive, so they make the electrode small and still charge you a fortune)

 

I've been using iridiums for over 20 years in forced induction applications with 2L 3L 4L 5L 6L etc...engines.

I've tuned hundreds of engines on coppers and switched to iridiums for longevity.

Copper plugs only get you to 12 to 20k miles whereas iridiums will get you to 100k miles

The spark is superior in iridium plugs based on experience, I know that Toyota 2jz-gte 3.0L at 550rwhp will start to misfire with a .032" Gap on NGK coppers
at 20psi of boost whereas when switched to iridiums the plug will support 800rwhp .032" on the same gap with 27psi of boost

There is nothing superior for high performance applications than iridium plugs. Unless using nitrous which is a whole other game with different rules.

People with bad experience using iridiums are complaining because they have not properly tuned the engine first. That is absolutely true about iridium- they foul very easy and impossible to clean, I have said so multiple times. You MUST fully tune the engine first before using them. It's easy to see who knows how to properly tune and keep an engine clean based on who complains about iridium plugs. Even closed loop tuned 14.7:1 will mark them up, 'brown' them up, I don't like it. I always run my engines 14.9 to 15.5:1 air fuel ratio to keep them spotless clean plugs.

 

good info where you mention copper misfires at .032” whereas iridium does not

You left out a key piece of info.
do you mean copper misfires at .032” AND BELOW ?

i see misfires on copper at or below .026” on my boosted 1993 with its optispark and msd-6 ignition

my point is you can think your tune is perfect.
then something beyond your control changes it (o2 sensor goes bad - as it did on mine). Now you are in deep doo-doo with iridium plugs

this is why i wont run them

 

I never use closed loop. I never use narrowbands. Those things are for people who do not tune their engine, they correct the tune for people who can't correct the tune themselves.
I always have a wideband in the car and I always know what it should say, and you can feel the engine run and listen and smell the engine, its behavior and these sensations are key to maintaining expectation and reliability. If the engine suddenly has some issue you should be able to tell right away from the sounds/smells/wideband for example. And by using quality components, i.e. fuel injector clinic or injector dynamics injectors, Properly installed wideband, properly pressure tested intake and crankcase, there is a big list of check items for performance engines which should be tested before trying to drive the engine hundreds of thousands of miles. And then you can rely on it and nothing will happen because you have done everything properly.

I am very careful and thorough, and when I set something up I guarantee it will 50k 100k 200k miles or whatever I know intuitively will attain. My engine currently 250,000 miles, I Put 50k myself at 600rwhp since 2017, did not disturb anything, same iridium plugs, Never Remove them, I know how they look even though I never removed a single one not even once.

 

If you have a motor that is tired and using oil, copper is the way to go. Iridium plugs will foul quickly while copper will go longer.