Cylinder misfire?

[62Comet]

Hi gang … I have a 62 Mercury Comet. The engine was recently rebuilt, with all the bells and whistles, including a new block, bored head, new cam, pistons, lifters, springs, and balanced. It has been relatively well maintained since then, but not very active. I recently encountered a loud banging from the engine and some stalling and traced the problem to cyl.3 … I replaced the plugs and noticed carbon on each plug and oil(?) on #3 … Unfortunately, I do not have the tools to do much myself. I am curious if it could be a bad wire from the distributor, or if there could be a more substantial problem … any help in this area will be greatly appreciated.