A tuning tale: BLMs say lean, plugs say rich

[XfireZ51]

Originally Posted by WARP TEN

This may be a little out of left field, but have you tried a slightly higher heat range of plugs? Maybe your plugs are running a little cool for your most typical driving and a change might show less discoloration. --Bob

Bob,

I had NGK 5 heat range in there. Not sure I would go any hotter. And the ground strap was indicative of the correct heat range for the motor. The plug coloration is inconsistent, w #2&4 showing brown to dark brown, nearly black. The other plugs on that bank were closer to “normal” w #8 being the leaner of them. The left bank was ok, maybe a bit lean, and all of that is indicated by the BLM split left and right. It averages out to 126-131 BLM, but that may be a 124 v 137 split as an example.
Frankly, the Autolites, which are a “projected nose” plug, puts the spark closer towards the center of the chamber volume. And the motor runs noticeably smoother w them. And it shows in the resulting MPG increase.
I’ll ohm the coils and plug wires next.
I’ll take it step by step and try documenting it here.