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Hi everyone, I am new to the 6 V positive ground system. So I apologize ahead of time for me seem like trivial questions. I have a 1948 dodge D 24 sedan with the 230 flat head six. She runs great at idle and all the way up to about 2000 RPM. Past that she start sputtering and Backfiring. I have rebuilt the carburetor, installed new points, condenser, rotor, distributor cap and set the timing. She honestly runs great at the lower RPMs. Once I start to accelerate or rev the engine from rest and get to about 2000 RPMs she starts to backfire and sputter. I have monitored the spark through my timing light And found that it starts to go erratic. I monitor the voltage on the positive side of the coil And at idle I have about 2.4 v. As the rpms raise the voltage drops and I find that the missing starts once the voltage hits zero and goes negative. Not sure what this means. I also used a test light to monitor the pulsing of the signal. The signal continues to grow brighter as the rpm is raised until I hit that certain mark. Then the pulsing is very erratic. It almost is acting like a rev limiter. But I cannot find one anywhere and my service manual makes no mention of it. I also must mention that monitored the vacuum with a gauge at the intake and have 20 inches at idle. If anyone has any helpful ideas I would love to here them. Thanks