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

Sometimes I changed on different vehicle from one sparkplug to another by different reasons.

In summary: Never change a running system.

Greets René

Quite so René. Our Rover V8 engines were specified BPR6ES, and the more modern plugs add nothing to the efficient design running of the engine; if anything, they may run hotter, although the biggest burn of "high spec" plugs is likely to be to your wallet. I've done 50k miles since changing my plugs 2 yrs ago, with no indication yet that they need replacing.

I changed the Iridium plugs on my previous Roadster at around 50k miles, no appreciable 'gap' wear at all, but did it anyway to keep the service history to spec, originals were Fomoco, replaced with NGK

Iridium must be very tough stuff as the inner core tip is tiny by comparison to normal plugs

Ultimately, its all about reliable spark. These fellas seem to have a good working knowledge,
https://forums.lr4x4.com/topic/81300-are-ngk-bpr6es-really-the-correct-plugs/
Interesting that the base plugs aren't as fussy about consistent higher voltage, as their dearer multi point\iridium tipped equivalents,
and all types seem to burn out similarly, especially if you're on a low mileage diet, which is probably 90% of Morgan owners.
Lower spec and more frequent replacement is probably the best\most economic way to go generally.

I have used Iridium spark plugs in the 4/4 and Lotus for many years. After changing the head gasket, my son screwed in normal spark plugs in the 4/4. I have to say, the engine runs super well, the plugs cost about 3€ each and I stick with the normal spark plugs. Changing them every 20 to 30,000km or so is ok. I even think (but it may be my imagination) that the engine sounds more throaty and pulls a bit better with the normal plugs. At least it doesn't run worse. I switched to Iridium in 2015, two sets since then, but I had forgotten that the normal plugs were so satisfying.

BTW I saw a new video from "Harry's Garage" yesterday where he starts his beautifully restored XJ 12 for the first time. Very worth seeing. The technician says that modern cars have spark plug change intervals that are far too long and that he definitely changes the plugs after far fewer miles.

But I have found another improvement. 1.5 years ago, I installed a new coilpack as part of a troubleshooting project. It was not the fault I was looking for, but after 80,000 km the new coil pack seemed more powerful than the old one.

A note about gaps and Iridium - which i use in the Sigma 4/4 and classics as well. Thing is, i experimented with my old Rover P6 ( 2000) which also has Iridium fitted, by increasing the gaps from "out of the box" to wider gaps in the hunt for a fatter spark. Mistake! The car ran perfectly but was a real pig to start/fire up when cold. Re-gapped back and starting is perfect again. The coil pack idea is a good one - not considered that before, as i'd assumed they either work or not. Might try that - a spare is always good.

I’m thinking of changing my plugs over Winter but am confused by the details in the owner’s handbook. They are currently Factory fit. I haven’t pulled them yet. Does anyone know the part numbers for both the Ford and NGK basic standard plugs? 4/4 Ford Sigma engine.
Thanks,
H

In my motorcycle spares business days over twenty years ago we sold a lot of NGK gold palladium tipped plugs. I thought I was honest in telling customers they offered little in the way of performance improvement compared to a perfectly set up ignition system with standard plugs. Their advantage though was the lower sparking voltage the finer tip allowed. Better starting therefore particularly from cold, and maybe better running when the chips were down. I never suggested they last longer than standard though. Indeed when removing a plug from my Moto Guzzi I could see the flame pattern orientation on the fine tip where it had melted slightly although the correct gap was maintained.

Iridium tips are the latest incarnation of this philosophy and I have one in my Velocette single which seems to provide very smooth idling. Too early to comment on longevity though.

With NGK coding the S suffix is replaced with V for gold palladium and IX for iridium equivalents.

I understood that the 3.7 V6 in later Roadster's has iridium tip plugs as standard but happy to be corrected.

Ive got a USA ski boat with a V8 5.7 litre Chevy engine. Had it for 10 years. For first 5 years I changed the NGK standard plugs every year. Had another unrelated issue with engine and engineer fixed it and then he recommended fitting Iridium plugs. They cost significantly more! Any way I fitted Iridium and got 400 more RPM , extra 5 mph and they have lasted 5 years so far!

Sometimes its the simple things that counts, I swapped a holly for a rochester quadraget once on a mercury v8 after all the faffing about my best purchase was uprated plugs and new leads. Rule no1 start at the basics first, Just about got to grips with that concept it took a while......