Spark plugs

[Forumadmin]

I thought it time to revisit the spark plugs fitted to the Javelin.
The original was Champion L10 (90 heat range or 17 car or NGK 3) but also the L87YC which is a colder plug. (87 heat range or 14 or NGK 4)
https://drivcat.com/overlays/part-detai ... brandId=CP

But asking what Champion now think should be fitted.
https://www.championautoparts.com/find- ... Brand=bbkh
which offers two types.
Plug Type L86C; Non-Resistor Type; Gap 0.022 (in)
Plug Type RL86C; Resistor Type; Gap 0.022 (in)

https://www.ngk.com/what-is-a-resistor- ... 0operation.
The 306 L86C spec
https://drivcat.com/overlays/part-detai ... l%20Engine

The L87YC is heat range 87 where as these are in heat range 86.

I usually fit NGK whose alleged equivalents are B6HS and BP6HS respectively. The latter is what I have fitted for 30 years and used for competition.

Reverse engineering from the Champion spec above gives a lot of alternatives so choosing the
https://www.ngk.com/search/reverseengin ... 312,165325
NGK 6326 BP6HS-10
NGK 7331 BP6HS
Comparing the two the only difference is the Gap .039" (1.0mm) .028" (0.7mm)
So my guess is that the larger gap might be suitable for electronic ignition sports coil.

BUT WHAT ABOUT HEAT RANGE?
https://www.ngk.com/heat-range-conversion-chart-2
This chart does not match up with Champion numbers but more research showed that 86 is for industrial engines and is the same as 12 for car engines!!! This is equivalent to NGK 5.
https://www.championautoparts.com/Techn ... range.html

The spec shows a heat range of 6 which is colder than the L86.
https://www.ngk.com/ngk-7331-bp6hs-nickel-spark-plug

So to get the original hotter range use a BP4HS or BPR4HS (with resistor if you have a radio fitted) .
The modern petrol may not require the hotter plug. The motorway driving may not suit the hotter plug.

But I think I will try the 4111 BP5HS which has been discontinued or perhaps the BPR5HS with resistor which is available as the Jav is not doing competition or lots of motorway.