NGK Sparkplug Codes
The codes take the form : [B] [CPR] [6] [E] [S] - [11]
Six fields, some of which are optional (eg the second)
Field one: Thread diameter. |
A = 18mm, B = 14mm, C = 10mm, D = 12mm |
Field two: Construction. |
C = hex size 5/8" K = hex size 5/8 with projected tip (ISO) M = compact type P = projected insulator type R = resistor SD = surface discharge for rotary engines U = semi-surface discharge Z = inductive suppressor |
Field three: Heat Range. |
2 = hot up to 10 = cold |
Field four: Thread reach. |
E = 19mm F = tapered seat H = 12.7mm (1.5") L = 11.2mm (7/16") If this field is blank, an 18mm diameter plug has 12mm reach, and a 14mm plug has a 9.5mm (3/8") reach. |
Field Five: Firing end construction. |
A, B = special design (no details given) C = special ground electrode G = racing use GV = racing use V type H = half thread K = 2 ground electrodes for certain Toyotas L = half heat range LM = compact lawn mower type M = 2 ground electrodes for Mazda rotary engine N = special ground electrode P = platinum tip (premium) Q = 4 ground electrodes R = delta ground electrode for BMW S = standard 2.6mm centre electrode T = 3 ground electrodes V = fine-wire centre electrode, gold palladium VX = platinum tip (high performance) W = tungsten electrode X = booster gap Y = v-groove centre electrode |
| Field Six: (after the dash) Wide gap. |
8 = .032" 9 = .036" 10 = .040" 11 = .044" there is no 12 13 = .050" 14 = .055" 15 = .060" 20 = .080" |
One tip for V6-engined cars is to add a "C" to the second field of the plug recommended for your car. The only difference is that the plug will have a 5/8 hex instead of a 13/16 hex. The smaller hex plug (and socket) is a bit easier to sneak down into the cylinder 6 spark plug well past the brake booster/master cylinder.
This info was provided by Paul Witek, on the Alfa Digest.
Maintained by Ben Dixon
