283 sputters at both ends
OK, narrowed it down I think. While timing the engine I decided to place the plug wire pick-up on other wires. I watched the light steady on some wires and skipping several flashes on other wires. This indicates that there is not a steady voltage going to some of the plugs. This will cause fuel to ignite elswhere on hot surfaces either through the intake or out the exhaust header. I traced it to the MSD factory distributor connectors on the new MSD wires to be defective! I also was advised from another classic car owner that he had the same problem and switched plug wire brands to sove his problem. Lesson to be learned..name brands are not always the best to buy. It can be a costly and time consuming experience.