Spark plug heat number ?

[krisgenchev]

Hi ! Me again ... How are you suppose to know what heat number spark plug you need ? Do you need colder do you need hotter ?
What should i run on my setup (in signature) Currently running BR7ES , I am looking to get Iridium so should i order 8 or 9 , keep it 7 ? Thank you. If there is a topic for that i apologize, try to find but couldn't . The engine runs at 87.0 C  or 188.0 F at WOT ,thats on the coolant sensor on top of the head, its been cold outside too.

[Rune 75]

For your cylinder BR8ES or B8ES is recommend. So go with 8.

[oldgeek]

I ran an 8 in my AC street race. I say give the 8 a try, as long as your temps stay where you want them. Don't be surprised if you carb needs a retune with the hotter/colder plug. For me, I have see it make a big difference on an AC cylinder.

[Zino]

If you are not fouling plugs and temps are good .
Your plug heat range is close enough .

When you go up in number Your cylinder temp will drop and get you closer to fouling.

Old Geek is right you may have to tweak the carb especially real cold / warm weather or for elavation.

[christopher]

Watch out on your plug temperature, the number moving up and down for heat range is by brand. NGK for instance gets colder with a higher number, Bosch is the opposite.

[Zino]

Christopher good point I am a ngk fan