Plugging away at the colour

[Rusty Spokes]

thanks for that Rusty.

x2 fckn great read, now im confused, it was written in 77 so is it pertinent to todays fuels"

Gordon was on the west coast and using unleaded fuels..most of the time. Now we have 10% ethanol mix fuels mandated in most of the USA.

Modern fuels burn very clean. If the spark plug heat range is good, timing is correct and mixture is correct..the plugs will have a very clean insulator, as Gordon explains. The mixture ring at the bottom is key.

If you let the engine idle with our old Dellortos..the plugs will get darker as the insulators are not as hot.

You need to do a clean plug check when checking mixture..shut the engine down and coast.