[Targalid]

I would remove that distributor, carefully blocking the hole in the engine with a clean rag, and give it a good cleaning. If it looks corroded where you can see it, you can only imagine what is below the advance plate. I did this with mine and was amazed at how much crud came out the bottom. You do not necessarily need to disassemble it to clean it. Various cleaning sprays are available that you can direct into the cavity and watch the dirt flow out. You can check your work by seeing the action of the advance plate improve. You can also soak the entire unit in a container of solvent if you remove it from the engine.