Spark Plug Quiz

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 http://www.oldengine.org/members/diesel http://www.stationary-engine.co.uk http://www.oldengine.co.uk

  Quoted Text Here  
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, http://www.laboutiquedutracteur.com/fiat I'm sure there's others who might help and supply the plugs needed.
John

John,
Your the ultimate Anorak.
Martin P
wrote:
  Quoted Text Here  
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, http://www.laboutiquedutracteur.com/fiat I'm sure there's others who might help and supply the plugs needed.
John

wrote:
  Quoted Text Here  
Nah, this is http://www.sparkplugs.co.uk/pages/technical/champion-code.htm
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