I currently have some NGK spark plugs which are one stage colder. A while back I came across a thread which had a formula or horsepower range for determining when a two stage colder plug would be required. I cannot find this thread, and I looked for this information on the Net but had no success.

Can somebody please tell me what the formula/range is for determining the proper plug? I have a feeling I should be using a two stage colder plug. Thanks in advance for your help!

 

Looking at the power you're making, I'd suggest a plug that's 2 steps colder.

 

Thanks, but how would you make that determination? Could I tell by pulling my plugs and seeing if they are fouled?

 

If I go with a plug that is 2 steps colder, I am thinking of these:

http://store.summitracing.com/partdetail.a...15&autoview=sku

 

stock plugs are heat range of 7 already.. you might want to look into Denso IK24, IK27 or colder.

 

Oops! So, is this one a 1 step or 2 step colder?

http://store.summitracing.com/partdetail.a...15&autoview=sku

 

ngk 8 series would be 1 step colder

 

I have NGK 9's in mine, as well as a buddy local to me with a 450hp laskey built motor.