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Friends with newer cars often insist on iridium spark plugs. Yesterday I had one more conversation of this kind, a friend suggested this type of spark plugs once more. I had a (quick) search in the web but I did not find an answer to the following question:

Is it worth the extra cost upgrading to iridium spark plugs on an M10 engine 1) on carbs and 2) without electronic ignition ?
Anyone done this ? results?

i dont think so because. No electronic ignition means you should run a smaller spark plug gap, iridium/ platinum plugs generally have a larger gap and shouldnt really be regapped.

Also they tend to foul up quicker because the electrode is alot smaller.

I would stick with copper plugs, gapped properly

Think Niall is right, even Bosch Super 4's (for example) might cause issues for the same reason, they perform well on electronic ignition though.

niall wrote:
Also they tend to foul up quicker because the electrode is alot smaller.

I was told the opposite, that they last longer than the other ones .. ???

they will last longer yes, when i say foul i mean especially with a carb engine, an excessively rich mixture, like when the choke is on in the morning, the electrode can become covered in black soot and cause a misfire. this will clear then when the mixture improves or with hard accleration

With copper plugs the electrode is much larger and can still fire from other parts that arent so sooty

Apart from that?
I mean, any improvements?
(acceleration? overall engien operation etc?)

In my opinion, No improvement. The main reason these plugs are used is for long service life.

Come on, do you really think there is such thing as tuned spark plugs for extra power? I do feel that there might be a hint of a more stable idle and midrange torque using Super 4's instead of regular plugs as they might reduce the chance of a misfire, but if that's fact it will not be much more than a hint.

I have no idea what sparks my mechanic puts on my car

I have to tell him next time at least to use these super 4's