Plug advice please

[tyasman]

I have a '70 S4, in Sprint trim with a big valve head. Weber carbs and set up to original factory spec. My (highly skilled) mechanic friend advised fitting NGK BP7EVX platinum plugs. They were fine on a trip to France this summer. However when I started the car recently she was running on 3 cylinders (or sounded like it), so I took the plugs out and replaced with the old set of ordinary NGK BP6ES. Ran perfectly. Which are the better plugs for my engine? I know the 7 is a hotter plug, but would this make much difference for ordinary road driving at 70/80 cruising speeds? Thanks for any answers.
Having seen the previous post from the EVO site I need to get out on the road again!

[miked]

I run the 6 plugs after having the same problem. If you search back you will see a few that do!

7's seem ok when giving it some!

Mike

[enskr]

I've been using BP6ES plugs for years - I find them mostly fine, but if I leave my S4 a few weeks without use in the winter it will often only run on 3 next time it starts. A wetted finger on the headers tells me which cylinder isn't firing, then changing the plug (for a new or old one) fixes it straight away - maybe you are experiencing the same problem, which is almost certainly unrelated to the temperature grade of the plug - my theory is damp ingress into the porous ceramic part of the plug, following a period of non-use.
I was going to try a set of the original Champion plugs to see if this would fix it but they were out of stock last time I changed them - anybody else got a view on this?

Kevin

[tyasman]

Kevin,
I think you may be right, the car has been standing for quite a long time, and has never done it before. I'll experiment by putting the old plugs back in after bringing them indoors to dry out. We went to the Classic at Le Mans last year and she never missed a beat - apart from the diff drying up somewhere in Flanders! Got her home OK with engine oil in the diff!

[richardcox_lotus]

Same thing happened to me a couple of years ago. Car OK when high-speed cruising on NGK 7's, but back in UK slower speed conditions I needed NGK 6's. I found the 7's would foul in traffic otherwise, making smooth driving very difficult. By the way, my understanding is that NGK number operate in reverse to Champion - NGK 6's are hotter than NGK 7's.

Also I've just had my engine back from a major rebuild & it now has Champion back in it !

[miked]

See old post and what Ed & Rohan and others say.

http://www.lotuselan.net/forums/viewtopic.php?t=1304

I agree about cold start after a long period of idle and one cylinder being off. I to feel the manifold (with rear of a finger, mine is wrapped) for the cold one. I understand that the heat range is about when a plug is up at temperature and it is not when you are cranking. However, I have had it happen more with the 7's. Could be wrong, but when running the 7's and finishing a run through town, I think you finish with more crap on the plugs. I found that it liked to go off No 1 plug with the 7's. Is this because No 1 gets more cool air around it? I had fouling with 7's when running through slow periods and not being able to rev properly. Used to have to clear its throat.

Bar my recent poor starting buisness , I have been using 6's and the car never misses a beat through town and also has no problems when on the bigger a roads.

Mike

[CBUEB1771]

I have always had good luck with Bosch W7DC plugs, the thread form is very clean and does not carve the threads in the head up. I have had bad luck with platinum plugs, I suspect they require a modern, high voltage ignition system.

[johnsimister]

With NGKs a higher number means a cooler plug, the opposite of Champion. So an NGK 7 is more likely to foul than a 6.

John

[chicagojeff]

i have found that the champion plugs foul a little less frequently than the ngk. Otherwise, performance difference was not noticeable. It always seems to be cylinder 3 for me that gets wettest from the aforementioned moisture syndrome.

Jeff

[tdafforn]

Strange world, I have found that the champions fowled more in my old worn out twink prioir to rebuild than the NGKs
tim

[steveww]

I have been using NGK BP6ES for about 3 years now with both modern city start/stop and track day abuse with out any problems.

[denicholls2]

Strange world, I have found that the champions fowled more in my old worn out twink prioir to rebuild than the NGKs
tim

On the Europa board, you'll find a similar discussion in the archives. It seems that some cars favor the NGKs, while others favor Champions. Oddly, both do it for exactly the same reason -- to avoid fouling troubles they had with the other brand.

I'm predisposed towards NGK from my motorcycling days (oddly, the same plug number in the bike as the Lotus). I've found on my S2 Europa, however, the same thing as my PO did: NGK's foul more frequently than Champs. I've got no explanation, it just is.

Doug Nicholls, 54/1822 Ma~

[rgh0]

I believe champions and NGK's of the same heat range run the same in the twin cam with the same predisposition to fouling or performance when fouled. In general for road use you need a hottor plug than Lotus recommend i.e. BP6ES NGK or N9Y champion versus the Lotus Champion N7Y recommendation

The reason I pefer NGK is that the insulator is much stronger and less likely to be cracked when removing the plugs. Trying to recover bits of cracked insulator between the plug body and the head recess is a pain and you dont want them to drop into the cylinder

cheers
Rohan

[pamitchell]

Would I see any benefit from running NGK BPR6EIX or EVX platinum plugs with my MSD ignition?
TIA
Phil

[rgh0]

The main driver for fancy exotic metal plugs and different electrode configurations has been emissions regulations requiring extended plugs lives in modern engines.

Life of a plug is goverend by two things

1. Electrode erosion - this is slowed with exotic metals and multiple electrode configurations

2. Deterioration of the electrode insulation over time due to fouling with deposits of carbon and ash from the fuel - modern fuel injected engines greately reduce this by keeping combustion conditions optimum at all times

With its carbs and varying mixtures compared to a modern fuel injected engine you will never get extended plug life with an Elan due to the second factor and most cars dont do that much mileage anyhow.

The exotic plugs give no better performance than an properly working standard plug in terms of power or fuel economy in real world terms.

So my conclusion ( for what its worth) has been that the increased price of the exotic plugs is not warranted on either performance or life ground so just stick with standard style plugs of the right heat range

cheers
Rohan