Resurrecting this old thread. I just had 7 of 8 NGK plugs fail to infinite resistance. Not good. Using B6S. They were too cold for my little motor anyway, NGK recommended the 3210 B-4 plug for under 8:1 compression. Does anyone know how the 216 compares in temp to teh 4, 5, or 6 NGK heat ranges? Looking for a 4/5 heat range in reference to the NGK world. Also wondering about the AC 43. What's working for folks these days? Please let us know what plugs you're using in your flathead and what compression ratio your engine is.
I've been running NGK B4L in my flatheads, its a little hotter plug than the B6L. I wouldn't use new champions either. I have a set of the Autolite 216's but I haven't ran them in anything yet, I've been sticking with the NGK.
I went to the B6S because its shorter overall - my valves were closing the B6L gap. The last set of 216s I bought were miss-matched from 2 different suppliers, so I shelved them. I have another set arriving today, so I'll give them a try, but i'm worried they'll also be too cold. I can't find any materials referencing their heat range.
I started a thread to see if anybody is running the autolite 275. Supposed to be hotter and 1/2" reach. I can't find the b4hs where iam. Sent from my XP8800 using The H.A.M.B. mobile app
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