My buddies 1990 5.7 IROC keeps killing plugs, New cap, rotor, wires, coil, and in good shape otherwise. But every couple of months it needs new plugs. When you pull them they don't really look like any I have seen before. Really black and discolored. Any ideas??

 

He's fouling out the plugs... I'm gonna be considered stupid by some for this (and I probably am...) but right now I can't remember if that's cause its running too rich, and not all the fuel is getting burnt, or if it's caused by oil in the cylinders.

 

Black and what color?? Oil comsumption probs?? Mods?? How fast will your bike go??

 

If the plug is shiny black then that's oil, if it's just black and not shiny that's carbon deposits. If it's oil, the valve seals are probably shot, if it's carbon then either the plug is too cold or there's work that needs to be done on the engine.