Whats the general rule of thumb for selecting spark plug heat range? We're trying to find a good plug for a 346 - 23x-24x cam ~11.6:1 CR making 485-505rwhp. I am leaning towards iridium "6s". And no this is not my motor. We're running TR7IX in mine.
Phil

 

on my 244/248 cam I have a .050 gap. If that helps.

 

Running TR55's gapped .045 in my 402 with a 248/254 629/622 113. 11:1.
I might be wrong though...but I just went with what worked before.

 

TR6's gapped .042>.045

 

If you guys could post your RWHP numbers that would be great...Hopefully this will end up as a sticky.
Phil

 

RWHP have little to do with plug choice. DCR, SCR and fuel used are the determining factors.

 

Very very true