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MG MGB Technical - Spark plug preferences

There are some comments under the fuel tank thread regarding spark plug faults.
As a result of a cracked insulator on N9Y plugs, I have changed to NGK. Has anyone else had problems with spark plugs? And what make do others recommend?
Robert
R J Collier

I had a N9Y crack on me last month. NGKs for me now too.
Steve Postins

I always used NGK BP6ES, I never had problems.
regards
michel

I even use NGKs in my lawnmower now.
Iain MacKintosh

I've always used NGL BPR6ES. Never had a problem with them......
Rob Edwards

NGKs are the best! Champion tends to foul easier. Most platinum plugs are subject to breakdown as well - the platinum tends to separate causing a misfire. I know its not that common, but it does happen. I've had new Bosch platinum plugs fail within 200 miles.

What heat ranges of the NGK are people using and in what "build" of engines?
Jeff Schlemmer

I never use Champion Plugs anymore. The Champion plug is made in two halves; often a plug can be open circuit from top to bottom. This doesn’t cause a problem if all plugs are the same (in fact plugs with a known gap used to be marketed as a way of ‘boosting’ the coil voltage. Also the theory behind some in-line ‘spark boosters’ that you see demonstrated at car shows etc.) however, to ‘jump’ the additional gap takes time, and if you have some open circuit plugs and some ‘normal’ plugs the timing will differ between cylinders.
Given any box of ten Champion plugs, about 4 out-of 10 are open circuit. Having talked many times to Champion in the past they don’t see this as a quality issue, despite admitting that the timing will be altered.
So…NGK it is, no contest.
MG Mike

NGK, I can't remember ever having to change one out of service interval over the last 20 years.
Stan Best

MGMIke
Very interesting comment.Do you mean Champion plugs
are of two different types even if they are the same model (eg N9Y) and you cannot tell them apart??
Robert
R J Collier

it was my plugs which are faulty 3 went down after about 1 hour running in garage no cracks found in plugs
is the reason why people use ngk because they are so readly avail anywhere but i got my n9y from usa pack of ten because they are so rare now
Ste Brown

Sorry I’ve not articulated myself too well. The Champion plug centre electrode is in two parts. The top part, which is surrounded by the insulator and connects to your HT ignition lead. And the lower part, centre electrode, where the spark is propagated at one end and which dissipate the heat to the plug along the body (copper core etc). These two parts are ‘touching’ but not electrically bonded. Something Champion doesn’t show in there cut-away drawings. It is this uncontrolled ‘gap’ that can give rise to same type/batch/set plugs having differing spark propagation times. I hope that helps in the explanation. If you have any N9Ys spare, check them with a continuity tester before using them, although, they could become open circuit once in use.
MG Mike

Nothing but Japanese plugs in my MG! I had a set of Champions fail me back in 1973 after 200 miles, caused me to spend a lot of time and effort because I did not initially suspect plugs with low mileage. Since then, I even use NGKs in my lawnmowers as well.

Joe

MGMike
Thanks for the explanation, I think I will stick with
NGK!!
Robert
R J Collier

Jeff. I use the BP6ES as a standard plug in both low compression engines and high compression engines (each factory or rebuilt back to approximately factory standard). If the engine is nearing the end of its useful life, i.e. oiling the plugs, I may use the BP5ES which is supposed to be a slightly hotter plug. (From memory--it has been a number of years now.) If the BP6ES seems a little to hot running, the next colder plug is in order. All of this is an experiment as each engine might well like a specific plug a little bit better than another slightly hotter or colder plug. Probably the only way to dial it in exactly is on a dynamometer/rolling road. Even that may not give an exact indication of the plug to use all the time. Up in cold weather country, when we drove our cars all winter long, we would fit one stage hotter plugs for winter use and standard plugs for summer use. Here in Arizona, a one stage colder plug might do well for summer use. No guarantees as to what any engine will do with any plug.

Les
Les Bengtson

I've been using Bosch Platinum on my car for years now. I've heard that they are unnecessary or I just flat out shouldn't use them (this from a tuneup tech seminar from a well-known mechanic), but never the reasoning for it. Maybe this spring I will switch to NGK, just to try it and see if there's a difference, but I feel I may be fixing something that isn't broken.

Oh, I have a 9.5:1 compression ratio, if that makes a difference.
Mark

Thanks for the info Les. I've been running BP7ES plugs in my engine for some time now. They always get a little sooty, despite the level of tune. I'll try the 6s and see how that works out. I may end up having to go richer than the #7 needles I'm using now if I use a hotter plug!
Jeff Schlemmer

Mark - take one of your Bosch plugs and measure the resistance from tip to tip. You'll probably find significantly more resistance on that plug than on an NGK non-resistor (BP6ES.) Probably in the 3-4000 Ohm range.
Jeff Schlemmer

I used to use bp7es in my 1995cc when I was doing a longish open road commute. They ran very clean. These days I drive 15 busy miles from cold, twice a day, and need the warmer bp6es plugs to burn the soot off, even in the outside cylinders.
Steve Postins

The 3-4k resistor on ony R plug is necessary for cars with modern electronics to quench high-frequency interference which can affect electronic systems on the car. They have negligible effect on the spark, typical resistor cable is many times that, and resistance of that order has very little effect on the microscopic currents of HT. NGK state "Because the resistance value is only approximately 5000 ohms, there is no detrimental effect on engine performance, power output, vehicle emissions etc. It is also a fact that many motor sport world champions only use NGK resistor spark plugs. In nearly all cases - apart from some very old low output ignition systems - resistor spark plugs can be used in place of the non resistor versions."

The rise time of HT current is extremely rapid and the additional time caused by any additional gap in the plug or anywhere else will be negligible, and in any case compensated for in dynamic timing.
Paul Hunt 2

I use NGK when possible. I have used nothing but resistor plugs for the past 30 or more years. I recently measured several different resistor plugs and they were all around 5k ohms.

Clifton
Clifton Gordon

Alright,what are NGK plugs?Who makes them?Thanks,Rich O
rich osterhout

Here ya go, Rich -

http://www.ngksparkplugs.com/about/index.asp?nav=20000&country=US

John
John English

That link didn't work. Try this one.

http://www.ngksparkplugs.com
John English

I'm running .040" flat top pistons nearly flush with the cylinder deck, and a 5 port alloy head with the Piper 270/2 cam which has retarded intake valve timing which really knocks the effective compression ratio down. The early style large combustion chamber has been opened a little to give flow to the outside edges of the valves. The ports have had a little modification as well. I'm showing 150+ psi at cranking.

The car runs good on midrange gas and puts out lots of power. NGK 8 es with .050" gap work great. The extra gap makes a big difference in cold running right after start up. I was getting all kinds of detonation with the 6 heat range.
No 3 looks richer than the other 3 cylinders. About 6000 miles so far and they look like there is at least that much more life left.

I would think with a supercharger you might want to go to a colder plug.

Barry
Barry Parkinson

I have only used the stock Champion plug for 20 years and hundreds of thousands of miles with zero plug issues. fwiw
Paul Hanley

rich osterhout - NGK is the manufacturer, a major one, in the same leage as Bosch, and probably bigger than Champion is now.
Paul Hunt 2

What plug was orginial to the MGB?
rich osterhout

Rich,

Champion N9Y is manufactures' specification.
Paul Hanley

NGK's!
I have used them for almost 30 years, in just about everything.
I have seen electrodes on NGK plugs worn to a point, and wide gap, and still run better than comparable (*&^% or ^&%$#@.

They have never let me down!
Doesn't hurt either that they partially sponsor MAC events.

www.mnautox.com

And we fly their banner at events etc.

SF
Dwight
DCM McCullough

Paul, you and I seem to be the only ones here using Champion plugs. I'm suprised to say the least!

I have also had no problems whatsoever with Champion plugs in the 6 MGs I've owned. I plan to stay with them.
Steve Simmons

steve
Aren't plugs a generic product? You either get platnimum long life plugs or non p. You choose the appropriate heat range. You choose resistor or not.

I broke an NGK plug checking my compression. I replaced it with a Delco plug, because that was the only plug the local parts store had in stock in that heat range. It made the engine go just like the other 3.

The guy at the counter told me that NGK was a really good plug. How does he know?

Is there really any meaningful difference? The new cars all use their brand. They all last 100,000 miles and give top power, mileage and pollution control. If one were better the mfg would be using it. Price is the arbiter.

My 2 bits

Barry
Barry Parkinson

I am with Paul and Steve. I have always used Champions in all my British cars for years and have never had a single problem.
Emmanuel Kafant

Plugs are a generic product and there is only a very small difference between different manufactures. But In my opinion plugs are as generic as tyres are; they all look similar in their construction, have to meet certain specifications such as thread size, electrode length & temperature rating, insulating properties etc.

So, personal preference also plays a great part in one selection and loyalty to a brand. On the B engine, the noted difference is not too great between any major brands of plugs. However, from experience of Champion Plugs that I have experienced during over 20 years of designing and manufacturing ignition systems, I no longer use Champion plugs, certainly not in any race car applications, and as a result of that, I globally use NGK in all my cars and recommend them to customers and colleagues.

One different make plug or one plug with a additional ‘gap’ DOES have an affect on the timing and therefore the running of the engine. The rise time IS greater, sometimes twice the period, albeit, in the 50-100microseconds, but the higher voltage, produces more electrical ‘strain’ on leads, distributor cap/arm, plug insulators etc. and actually produces a lower current, shorter duration and weaker spark. All of the above WILL have an adverse affect on the timing as the one ‘odd’ plug will tend to foul easier, produce a spark that can literally be blown-out, prematurely strain the insulators, (you can sometimes see the corona around the plug base!) and therefore affect the timing on that cylinder. Now on a stock B series, you may not notice in normal running, apart from having to replace some of the ignition components more frequently and the occasional hesitation or ‘cough’ when overtaking/pulling away/ under full load. (The B series actually benefits from different timing between 2,3 and 1,4 but that’s another story!)

To those still using Champion plugs, I recommend that at your next service you try a set of NGK plugs, providing your ignition system is in tip-top condition, I’m sure that you will notice the difference.
MG Mike

Ste Brown admits to the plugs "going down" after about 1 hour of running in the garage. I would suggest that the plugs haven't gone down at all but have fouled. Now these are fairly dirty running engines and it is very common for plugs to foul unless they are being operated at normal running temperatures. The water temp gauge may indicate normal but combustion chambers will be far below normal and not high enough to keep plugs clean unless the car is on the road. My advice to you would be to take the car out and you will find that within a very short space of time all the plugs will clear. Whilst I use NGK plugs I have used Champion for years in the past and would have no hesitation in doing so again.
Iain MacKintosh

iain
i cant take on the road not ready
yes the plugs had fowled as we were setting up the carbs
my dad said same as you
but one plug went down within 5 mins of replacing and the plugs we have in have been fine
i will try another box of plugs we have as ive had no probs before on other restorations so could be either fowled or just a bad box
Ste Brown

There is a similar thread running on the midget section of this BBS and there is a similar theme on there. NGK plugs for the majority of the contributors on there, me included in both Midgets and my BGT.

I don't have a clue as to what makes them better, all I can say is that two different race engine builders (that I have used) in completely different parts of the country both use NGK. So that's what I use in the road cars now.

Andrew.
A I McGee

This thread was discussed between 14/02/2006 and 21/02/2006

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.