1962 Corvette 327 Engine - The Return Of "Patti's Daily Driver," Part 2 Photo Gallery
The silver stuff on the threads is Joe Sherman's antiseize. The light black around the circumference is from the unleaded gas, says Sherman. Hopefully, you can see a slight discoloration at about 60 percent up the electrode from the far end. Sherman says this is how you correctly read a spark plug. A discoloration at this spot says that jetting and combustion are both excellent.