[Formulajones]

Ive said that a lot Steve, referring to your last sentence. Unleaded fuels, especially those with ethanol, are not that good at coloring plugs as we used to see them with good ole leaded fuels. So it really starts to become a pointless exercise

Like cliff said, I find it better and easier to just give the engine what it wants. Drivability is more important and it doesn't always agree with what someone thinks it should be.

I like using a dyno for wot to get it in the ball park. Mainly just to make sure it's safe, but like cliff said you won't find a ton of power with big swings in afr. Anything from say 12.2 to 13.0 on an N/A engine won't really make a big swing in hp. Now if you're way out in left field then sure, that's a different story. At the track D/A conditions might make you take a big swing at it. But drivability tuning just comes from experience. Give the engine what it likes. Plug reading with unleaded fuels can be a bit misleading when it comes to fuel mixture.

Timing marks and studying the porcelain for specks can be useful however.

To really read a plug properly you either have to cut the plug apart anyway, or you need a lit magnify eye piece to really look down in there. I doubt anyone here even goes that far. Just pulling a plug out and looking at it is barely half the story anyway.