Spark Plug Quiz

Jul 18, 2008 3 Replies

Had an email from Oz, the owner of a Fiat tractor wanted to know what spark plug to fit.



I couldn't find anything on the web, so asked what he had already fitted to the engine.



"there is a champion rn12yc,b8es-njk,njk-br9es,champion-n8..i bought it from a lady who's dad passed away and i do not know what plugs to put in."



So we have:



Champion RN12YC NGK B8ES NGK BR9ES Champion N-8



What did I recommend and on what basis was the choice made ??



The N-8 is equivalent to an NGK B6ES



Peter



-- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk

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I'm not sure about NGK numbers. Champion N8 is a fairly soft, non extended nose, 14mm plug. 8 is the temperature range. BMC A series used N5's before going to extended nose plugs. RN9YC, R =3D resistive for RF supression, N =3D 14mm thread as N8 above, 9 is the temperature range but isn't directly comparable with the N8, Y is extended nose, C is copper cored central electrode. If there was another C, that would be a copper side electrode. The temperature ranges cannot be compared across these two plugs unfortunately. BMC A and B series used N5's before going to N9Y's. The extended nose puts the electrodes into the cooling effect of the cylinder turbulence.

The BR9ES is probably a resistive plug. I would avoid these, they're not needed unless there's a modern stereo or 2 way radio fitted. Even if there is, I would try it without first and only go that route if there's a problem.

How old is the tractor? The older they are, the lower the compression ratio and the softer (hotter running) the plug that's needed. My 1949 Ferguson T20 runs about a 5.7:1 CR and uses an Champion N7 plug. I would suggest that equates to a N12Y extended nose type. I've noted the NGK equivalent for the tractor is BP2ES but I can't remember where that info came from.

Google found this site,

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'm sure there's others who might help and supply the plugs needed.

John

John,

Your the ultimate Anorak.

Martin P

I'm not sure about NGK numbers. Champion N8 is a fairly soft, non extended nose, 14mm plug. 8 is the temperature range. BMC A series used N5's before going to extended nose plugs. RN9YC, R = resistive for RF supression, N = 14mm thread as N8 above, 9 is the temperature range but isn't directly comparable with the N8, Y is extended nose, C is copper cored central electrode. If there was another C, that would be a copper side electrode. The temperature ranges cannot be compared across these two plugs unfortunately. BMC A and B series used N5's before going to N9Y's. The extended nose puts the electrodes into the cooling effect of the cylinder turbulence.

The BR9ES is probably a resistive plug. I would avoid these, they're not needed unless there's a modern stereo or 2 way radio fitted. Even if there is, I would try it without first and only go that route if there's a problem.

How old is the tractor? The older they are, the lower the compression ratio and the softer (hotter running) the plug that's needed. My 1949 Ferguson T20 runs about a 5.7:1 CR and uses an Champion N7 plug. I would suggest that equates to a N12Y extended nose type. I've noted the NGK equivalent for the tractor is BP2ES but I can't remember where that info came from.

Google found this site,

formatting link
'm sure there's others who might help and supply the plugs needed.

John

Nah, this is

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I can't claim all the credit for finding it, the details were posted on another NG. Interesting site though. All you ever wanted to know about spark plug numbers and more. I can see hours of endless amusement here.

John

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