The plug residue was at the top of the plugs, in the wire nipple, not at the tips. The plugs seemed normal, but were definitely worn, so I replaced them. Engine temp is okay - right around 180, where it's been.
The carb is a W-1. It hasn't been rebuilt since I put it on the road in 2008. Whether the previous owner rebuilt it, I can't say.
Good point about the valves. I haven't adjusted them since the truck was put on the road in 2008. I've got maybe 5,000 miles on it since then. Would that cause the dramatic loss of power and gas mileage? I forgot to mention the mileage. It's down in the 10.5 range now, where it was 14.75 before.
Thanks for your help.
