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MG MGA - Iridium Spark Plugs - Any good?

Hi guys,

I have seem some new, super sexy NGK Iridium spark plugs for sale on the mighty Ebay that promise oodles of extra performamce, longer life, etc., etc.

Are they any good? Has anyone had any experience with them? Should I just stick with bog standard plugs? What do you use?


Grant :-)
G Hudson

I think they will give you another 20 BHP, then add 3 angled valve seats for another 20 BHP and then Kand N filter for another 10 BHP, ram pipes are a must for 10 BHP and finally an extractor manifold and suddenly you have doubled the power of the engine. NOT.

They talk a good job dont they, but stick to simple things and you won't be cheated out of your hard earned cash. NGK BP6ES will give you all the performance you need IMO.
Robert (Bob) Midget Turbo

Grant, my MGA isn't far enough along to put spark plugs in it yet, but I have used platinum plugs exclusively in my daily vehicles for at least 25 years. No experience with iridium plugs, but the platinum plugs last 4 or 5 times as long as normal ones. If they are anything like platinum plugs, I say give them a try.

I honestly can't speak to performance since I haven't ever compared them to regular plugs, but pinging has never been a problem with the platinum ones.

Let us know if you try them out.
L Wheeler

As L Wheeler said. The advantage is long life, NOT performance. Both Platinum and Iridium plugs last longer. The electrodes don't erode as quickly as normal plugs. In some modern cars it takes hours to install plugs. That is why they need them. I once again find myself in agreement with Bob. Use NGK BP6ES plugs. Our cars are more susceptible to plug fouling and the fancy plugs don't help in that area anyway.
R J Brown

Hey, that'll be why the MGF has fancy platinum plugs, you have take half the car apart to get at them! Did you ever work on one? It's like trying to fix your car through somebody's letterbox (or is that mail slot)! Give me an MGA every time and plugs you have to clean and adjust every 5,000 miles.
Lindsay Sampford

I have used lots of different types and brands of spark plugs in my MGA over the years, and they all work pretty much the same for function, performance, fuel economy, etc. So for many years I was using whatever was cheap and conveniently available, which was usually Autolite 63 non-resistor type from the local NAPA store for about dollar each. Also see here:
A high compression race engine might need a little different heat range, but they're still cheap. Being cheap and easy to change in the MGA it's hard to beat the price/value.

I would avoid Champion resistor plugs like the plague. It has been my experience that about 10% of them may be bad right out of the box with far too much resistance, and others may fail in short service for the same reason.

I tried Platinum plugs for a while, purchased at a local discount department store for about $4 each. I don't recall the brand name, but they kept cracking the ceramic insulator off the tip in #1 cylinder, so I gave up on those. They might have been too high in heat range. Excessive spark advance is not an issue in my car with low compression.

Several years ago a club friend gave me a set of Halo spark plugs (see attached picture). He was selling the things, and he wanted me to give them a long test run in my MGA. I suppose he was looking for a rosy review to help sell the things, but I told him up front I don't play favorites so don't expect much. My original expectation was that the things might have a very long life, but otherwise no (noticeable) difference in function vs any other plugs.

They have been in my car for just over 50,000 miles now. I have never touched them except for occasional inspection during routine service. They have been working fine, running that nice sandy tan color for me, and they will stay in the car for as long as they continue to work. Even if they might last forever, that would not justify the price tag for me around $7 each.

Subsequent research has shown no upper limit for useful life if the Halo spark plugs, some having run over 100,000 miles, so maybe they well last forever. You can check out the following link for detailed information about Halo spark plugs. Keep in mind is is from the manufacturing company, so as nifty as it sounds it may not be revealing opposing commentary.

Barney Gaylord

They're some neat looking plugs Barney, never seen anything like them! I guess if you put them in an MGF you'd be keepng the plugs and changing the engine!
Lindsay Sampford

Let's see if this reactivation thing works. I just finished the testing of the Halo spark plugs, 10-1/2 years and 73,000 miles. Kind of disappointed they didn't make 100,000, but such is life. Full details here:
Barney Gaylord

Iridium plugs are said to require lower HT voltage for spark, and they do last quite a long time; over 100,000, but I've never run more than 117,000 on a set, so I don't know their full life. I do know that they still looked very good.
Mike Parker


How do you adjust the plug gap on those Halo plugs?

Steve Gyles

You don't.
Barney Gaylord

The gap starts at .025". As the center electrode burns off the sharp corners, the spark takes the shortest path from a point less burned, so wear progresses evenly all around. The ring (grounding) electrode is far larger than the center tip, so wear on the outer ring is nearly nil by comparison (where ordinary plugs commonly suffer as much wear on the outer electrode as on the center tip). The center electrode has to burn back quite a lot before it increases the gap very much, which is why they last so long. There is nothing magic like platinum or iridium electrodes. It is just low tech that is very robust in design.
Barney Gaylord

Barney's warning for Champion plugs is right on the money. Mine, brand new out of the box were arcing in a very colorful way. Avoid Champion.
David Holmes


that's really useful! I've heard mixed things about Halo plugs and I'll take your points as the usual gospel.

Also, thank's for confusing the hell out of me - I thought this was an old post - and it was! ;-)

Clearly the reactivation thing does work.

all the best,

Grant :-)

PS just to say that I went for the iridium plugs as I got a good deal (and got a spare pair of normal plugs). That was nearly 4 years ago, and the car should be going to be tuned in the next month, and there really is a strong risk of 942 ABH finally making onto the roads this summer!
G Hudson

is there a problem with manufacture of the Halo Plugs, their site says most models not available for 9 months?
Ross McIntosh

This thread was discussed between 05/06/2009 and 24/01/2013

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