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MG Midget and Sprite Technical - Correct Spark Plugs

Dear Members,

I am sure this has been asked before, but I cant find a corresponding thread in the archives - so I am asking everyone confident enough to answer:

In the original Manual it says N5 spark plugs are the correct type for the 1098cc engine. Since I want to be close to original specs I try to find the right plugs.

When I look at the heat rating between Champion and NGK this would correspond most closely to a BP7ES today (currently I am using BP6ES or BP5ES).

I am interested in opinions, recommendations and experiences.

Thank you.

WB Bankowski

I would use BP6ES for road driving, if they seem a little weak looking on inspection go down to BP5ES. We use BP7ES for competition.
Peter
Peter Burgess Tuning

It took me 30 seconds to find it in the archives. I searched "spark plugs 1098", "all of these words" in technical.

Result.

" --Thread: spark plug change

Posted 23 September 2003 at 15:01:00 UK time
Mario Belcastro, Pennsylvania, USA, mbelcastro1@home.com --- I have a 63 1098 cg engine,that needed a valve job.So i got 1275 valves,springs ,guides,and hardened seats.Also upgraded to a petronix and performance coil.While i was at it i installed the larger 1098cc exhaust and manifold.The question is do i change my rn5c champion plugs to the n9yc champions gapped at .030, or go to somthing like ngk bp6es.The car is properly tuned but tail pipe is sooty.Seems it should run a touch smoother.Any suggestions would be appreciated.


Posted 23 September 2003 at 18:03:33 UK time
Bill, Small dark green pleasure machine --- Personally I'd go NGK anyway, haven't liked the Champions much lately.


Posted 25 September 2003 at 06:04:57 UK time
Marc Judson, California, USA, marcjj@earthlink.net --- "Sooty" exhaust pipe usually means too rich a mixture or burning oil. The larger manifolds might require the carb settings be revisited. With all your new guides and valvs any oil in the chambers would probably come from the head gasket or rings. M -- "


So there you have it. BP6ES has been the way to go for as long as I remember, if you don't like champions. Although I used to used champion copper cores and never had any trouble, but for some reason they became more expensive than NGK. I have a box of NGKs(nos) that I picked up very cheap. I doubt I'll ever get through them.

P.S. mine's a 1275, but they all work well on bp6es






Lawrence Slater

Thank you for the info, that really helps me.

Can someone tell me what would happen if I use BP7? They are even colder than the 6. Would the head get too hot?

I have been using a set of the BP6 for a week now and I seem to get "operating temperature" sooner than before...
WB Bankowski

That may be to do with the weather, rather than the spark plugs.
Dave O'Neill 2

7s may well foul up, 6s will run at the correct temperature ( we are talking plug temp not engine temp). If the plug runs too cool it may well clog up with soot and then short out. This i very common on race plugs such as 8s when the engine is cold too. Some folk use say 5s or 6s to warm the engine then put the 8s in for racing. If they run the 5s or 6s in the race they usually ruin the engine as the plugs run too hot and cause detonation!

Peter
Peter Burgess Tuning

Peter,

thank you for your explanation.

I hope I am sounding to foolish, but my intention was to control engine temperature a little by changing onto cooler spark plugs, especially for highway driving (65mph average).

Since summers are rather hot here (30+ Degrees average, July/August even more), I thought this would help a little in preventing engine overheating.

Good or bad?
WB Bankowski

The plugs will not alter the overall running temp. Fit a bigger radiator and/or better rad shrouding to increase airflow through the rad if you need to improve cooling, whatever you do don't use waterless coolant!
The cooler plug runs cooler around the electrode only but if it is too cool the plug will foul. The plug grade needs to be correct to suit your combustion requirements.

Peter
Peter Burgess Tuning

I have gone to AC delco rapid fire ugs over the NGK, I really like them, they dont appear to foul as easily as the NGKs, which the NGKs are better then the champions in my opinion

Prop
Prop and the Blackhole Midget

Peter, thank you for the explanation. Indeed I had thought from reading on the web that spark plugs could "draw away" heat from the head - I must have misunderstood that.

Why would waterless coolant be bad for the engine?
WB Bankowski

Because the engine tends to run 12 degrees C hotter and cannot reject heat as well as water does!
Peter
Peter Burgess Tuning

Peter
I suppose that for the purposes of track days at high speed circuits like Silverstone, one should treat that as if it were competition (long straights and high revs).
Chris Hasluck

Sounds like a good plan.

Peter
Peter Burgess Tuning

This thread was discussed between 27/08/2015 and 07/09/2015

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