So I am going from a static compression ratio of 8.5:1 to 11.5:1, the stock NGK is a BPR6ES, the next heat range cooler is a BPR7ES but I cannot find these available readily. I can get the BPR8ES this plug is two stages cooler, would this plug be too cold? This engine will only be seeing high rpm race use. NO street use at all.

-Joel

 

Try the 8. My guess is that you would want to go at least that cold. I would recommend maybe even trying a 9. Run the 8 and check for detonation.