I need the brain trust on this one. I have an IO-320 B1A in my -9A with dual LSE plasma III ignition and 9:1 compression pistons. I am not the builder. The original builder ran NGK BR8ES plugs but Klaus "told" me to run the Denso IK27. As far as I can tell, the Denso is slightly cooler plug than the NGK 8 heat range. I'm just going by the charts I can find on Professor Google. Before my trip to the Caribbean in March, I put in all new NGK BR8ES plugs. They now have approximately 100 hours on them. I fly LOP, as a practice. Took the plugs out today as I'm going to do a compression check and they're all black, making me think the plug is too cool a heat rating. My confusion is that my pistons are 9:1, not 8.5:1 so, if anything, they really should want a cooler not hotter rating, right? Can someone give me some knowledge and guidance here?
Thanks in advance for everyone's thoughts,
David