Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Iridium spark plugs

I agree with Richard, the red colour is most likely from fuel additives. I noted it last year on my motorbikes, normal insulator colour before any additive used and pink on the insulator when using additives.

Yep, Totally agree with TBM. That is a sign of a perfectly set up engine and all four plugs should look very similar. As engines wear, and nowadays we are talking starship mileages on well maintained engines, you will probably notice some difference to no. 1 and no. 4 plug and the same to the tops of the pistons. This doesn't mean you panic and expect an engine rebuild! Rather time to check the individual cylinder pressures and if they are within the acceptable range carry on!

By the way I also agree that the gap looks way to big. That will really strain the coil pack, Overheating it and an eventual failure of same. It also leads to premature erosion of the plug electrode (iridium) thus increasing the plug gap further to the point where the electrode becomes something resembling a copper tip plug ( fine tip totally eroded )and the spark finds it very difficult to leave the electrode by way of these two effects and that's a guarantied situation to blow the coil pack.
Ford had no end of trouble with the Duratec plugs and packs and after putting their heads to the problem resolved all issues with a 1.0mm 39th/in plug gap. At one time these 100,000 mile plugs were achieving less than 10,000 miles and dealers had reverted to copper tips and would change the plugs on a car in for service if it had exceeded 6000 miles regardless of the plugs fitted! No need to panic though, Iridium are certainly superior if only for the quality of the spark which creates a cleaner burn and will help starting in extreme conditions. Probably we'll only notice as the nights get colder and we suffer condensation in the pots. Most of us will change the plugs regularly anyway, especially when you see the rusty plug bodies on removal so putting it into perspective there's not such a massive difference in price when were talking about maintaining an average priced car of £50,000 so just fit them regardless!

There is just one further thing to be aware of with iridium plugs, if the gap is too small do not use the electrode as a base to lever the earth/ground arm outwards. You can get a special tool or use snipe nose pliers in a gentle wrist twisting action then reset the gap.

Folks, many thanks for all the responses to my questions. Really informative and very reassuring.
Now I'm off to find my feeler gauges and reset my plug gap to 1mm!
That's the sort of job I can handle.....Simples!😁

Thank you Richard, very kind of you to provide a link!