Spark Plug Upgrade

[streetracer75]

I need to replace the plugs in My Simca 1200s and fancy fitting a platinum or iridium plug. Has anyone fitted iridium plugs to their 60/70's classic and got any advice? I've read they run fine in a older classic vehicle?

[austinpowers]

I have iridium plugs in my Trabant, and have had no problems over the last year that they been fitted. I went with Denso plugs and used the info on their website to work out which ones I needed.

[welshpug]

waste of money, standard NGK plugs of the appropriate heat range will more than suffice, i.e if its bone stock then whatever is in the ngk catalogue for that engine is what I would use, if I've bumped the compression up a bit them go up one or even two in my case.


by up I mean digit, which actually means cooler plug.

[streetracer75]

Yeah I hear what you say. It's just that I have fitted electronic ignition with an upgraded coil and thought if I upgrade to a precious metal plug I might squeeze a bit more benefit from the electronic ignition?

[melle]

I agree with welshpug, if you have an otherwise standard road engine it's a waste of money. Fitting performance parts to a standard engine doesn't automatically mean performance will improve.

[Ritchie]

I always felt that iridium plugs seemed to be a bit unreliable with carbed engines and they really don’t like being flooded.
As mentioned, personally I’d go with the correct NGKs.

[dodgerover]

With an upgraded ignition system then it's probably worth a go. We saw a marked improvement running iridium plugs in a Rover V8 still running standard points and condenser, that was running on LPG rather than petrol so no risk of flooding BUT 2 stroke MX bikes have run fancy race plugs for years and it's rare to get plug issues with those.

[vitesseefi]

Might be worth trying the multi-electrode plugs with 3 or 4 earth prongs. Though intended for long life not performance I have found that they work really well in some older engines. Triumph pushrod engines definitely like them and so do the older VW 8v water-cooled. I think it has more to do with the side electrode design rather than the number of electrodes. They are fairly cheap too. Although NGK do do them I prefer Bosch as I’ve had problems with NGKs failing if the insulators get wetted by fuel flooding. This on ordinary single and triple electrode plugs. I’ve not had great results with fancy plugs on older stuff even with high energy ignition. All you really need to do to take advantage of that extra voltage is to open the gap up a bit, but be aware that this will tend to find the weaknesses in you HT system components.

Nick

[swampy76]

Sept 9, 2020 19:59:28 GMT vitesseefi said:

Might be worth trying the multi-electrode plugs with 3 or 4 earth prongs. Though intended for long life not performance I have found that they work really well in some older engines. Triumph pushrod engines definitely like them and so do the older VW 8v water-cooled. I think it has more to do with the side electrode design rather than the number of electrodes. They are fairly cheap too. Although NGK do do them I prefer Bosch as I’ve had problems with NGKs failing if the insulators get wetted by fuel flooding. This on ordinary single and triple electrode plugs. I’ve not had great results with fancy plugs on older stuff even with high energy ignition. All you really need to do to take advantage of that extra voltage is to open the gap up a bit, but be aware that this will tend to find the weaknesses in you HT system components.

Nick

Back in the day when I had my MG metro I had the engine rebuilt by a family friend and well respected race part supplier Cyril Wilcox

Engine had modified valves, flowed head , Kent cams etc and to get it running right meant time on a rolling road at Hi tech in Cradley Heath .

This was about the time the splitfire plugs were coming on to the scene (purchased at mini in the park at Blenheim palace I think )
Any way he got a good figure out of it but thought it should run a bit better , reprofiled needle , yellow dash pot spring etc but he still wasn’t happy

Ripped the “fancy” plugs out and fitted a standard set of NGK, flat spot gone , emissions improved !
No more fancy plugs for me

[streetracer75]

Bit of a minefield this isn't it... As I say my initial thinking behind fitting a precious metal plug was that it might work well with the new Pertronix electronic ignition set up? All things considered I might just play safe and  stick with the stock NGK replacement

[melle]

You could always try for yourself (like I did years ago) and form your own opinion? To be honest, it's a bit like asking what oil or tyres to use; everybody has their opinion and hardly anyone has scientific evidence. Apart from that, circumstances differ wildly, so what works for one may not work for someone else.

[dodgerover]

^^^ this, fancy plugs into Rover V8 big difference, same style upgrade plugs into V6 Isuzu no difference.

[Ritchie]

Thinking a bit more about this, there’s probably too many variables such as plug location in the head, compression ratio and combustion temps with different engines to take into account to form a definitive answer, so it really would be a case of suck it and see.

[melle]

I agree with Ritchie, but I would add that most road engines have originally been designed for "standard" plugs, so at least those should work perfectly fine.

[streetracer75]

You know what your right, while it may cause more problems then benefits, for 4 X £8.00 it's with a try and experimenting. I remember years ago I fitted a Bosch upgraded plug into my Amphicar which the owners club were pushing (which is essentially a Triumph Herald engine) and they worked a treat. Still have them fitted today in fact.

[ChasR]

Sept 9, 2020 13:17:01 GMT dodgerover said:

With an upgraded ignition system then it's probably worth a go. We saw a marked improvement running iridium plugs in a Rover V8 still running standard points and condenser, that was running on LPG rather than petrol so no risk of flooding BUT 2 stroke MX bikes have run fancy race plugs for years and it's rare to get plug issues with those.

That is more down to LPG needing to be fired better and it battering the plugs ; LPG has zero lubrication.

We noticed this when we used to convert the cars. The cars that came with platinums were OK. The ones without? They'd be misfiring within 5k miles.

Two examples now come to mind:

-Jaguar XJ40 XJR 4.0. This had a nasty Mixer system to be fair. After 4k miles it would misfire and try to cutout. A new set of plugs had it OK again
-2009 Vauxhall Vectra 1.8. This got to the stage where it was doing 5k miles and misfiring again with plug changes. A set of NGK Iridium plugs (I think these were the LPG editions where both the electrode and the tip are Iridium coated) had them not leave the car again until the service schedule.

But back on track .

It depends on your mileage. I know Wards have said they've noticed Spark Plug erosion on alot of engines they've seen, which they reckon is down to the increasing ethanol content. So much so that they recommend changing the plugs at 10k now in Stags. Iridium plugs can get around that problem.


So it's depends on you really. If you want a little more piece of mind, go with them, otherwise, stick with the cheap and cheerful plugs .