I am in process of doing some work on my T engine. I removed the plugs and here is what they look like. Number 1 and 2 looked showed normal use [light tan]. Number 3 and 4 looked like they were just taken out of the box and never used. I do run a Z head and the car runs great. My best guess is a head gasket failure. Any other ideas?
Steve ; # 1 is always darker as # 2. # 4 is the lightest one. That has something to do with the intake manifold.
I have an idea, if the car runs great, why are you worried about the color of the plugs? Are there any other symptoms that concern you?
Perfectly clean white insulators is a good sign of water leaking into the cylinder.
You want the plugs to be somewhere in between light brown to grayish tan. However, slightly white may not be too bad unless it is "chalky white."