MSD Distributor Issues

[66AC]

These marks or carbon build up near the distributor posts often indicate a faulty arc from the points (unlikely points as you have an MSD dissy) or rotor to the plug wire post contacts. There is quite a lot of voltage jumping off the rotor into the posts of the distributor. In some cases where there is just a light carbon deposit, a fine sandpaper or crocus cloth can be used to clean off the carbon. Be aware, though, that too much filing will create too large of a gap on the posts and rotor and result in exaserbated further arcing problems. So in general it would appear that some arcing is going on to cause carbon inside the cap. It may be time for a new MSD cap and rotor, in my world, when you change the cap you also change the rotor at the same time. Also you may want to change/inspect your plugs and spark plug wires and connections. But I would start with the cap and the rotor. Also check the fitment of the cap, make sure that when it is attached (clamps or screws) that the cap is stable, and firm and does not rock or move in any way. In addition, you could take the cap off and try to wiggle the rotor. There should be NO play in the rotor. If there is any wiggle then the distributor will wiggle under RPM and not sweep the rotor in a consistent manner. That could cause arcing. For replacements, I would stay with the MSD brand. Just my two cents.