5 replies to this topic

[bluemini1979]

I have just got hold of a 7 port head for my build that is the same as the Pierce design. It has had some work done to put the larger valves in. My question is does anyone know what spark plugs these take as the hole for the plug is smaller that a standard mini plug. I know they have roughly 3/4 long thread.

Thanks

[GraemeC]

Are they not 10mm bike plugs?

[bluemini1979]

I believe so. Seem to be ngk er9eh
Does that seem correct? It’s just what google is saying when searching on there

[Shooter63]

Grade 9 NGK is a hard plug, a std mini uses 6 you might find you have fouling problems with them

Shooter

[mini13]

as above, you'll oprbably want 6's or 7's, 8's used to foul even in my turbo motor.

[bluemini1979]

I did think 9’s would give fouling problems does anyone know the number for 6’s with the small thread?

Thanks