Originally Posted by yragat
I bought a car with a 1960 390 Cadillac engine. The plugs are a little sooty (black,but dry) so I thought maybe I would go with a higher heat range. The book calls for AC 44 so I bought AC45. BUT the plugs that are in the car are Champion RJ12YC which does not cross reference with AC44. AND the champs have a longer reach electrode. I'm wondering if this longer-style plug was used for a reason,or just a mistake--Would there be any advantage using a longer reach plug?
I think I might begin by correcting the problem, too much fuel into the motor. Carburetor needs to be rebuilt, float level and float drop set and fuel pressure checked. What carb is on the motor?
Extended TIP plugs might aid combustion. They won't hurt anything, but be cautious that you don't use a plug with longer THREADS inside the chamber. The threads can glow red hot from the heat of combustion and light off the incoming mixture before the spark plug fires, causing detonation.