Had a strange problem last week on my 66 Charger, 383 w/Mopar performance electronic ignition retrofit. Maybe someone else has had this issue... Was running fine for years now. Drove it one day last week all fine. Two days later, started up fine, idled fine. After short warm up, backed out of garage into street and upon slow acceleration, RPM's dropped off radically and came back up. Put it in park, revved it up a few times, same condition. Tach also bounced radically to zero and back up when this happened. Still idled fine though. Drove around the block with engine doing this surging occasionally, but not always.. Back into the garage. Did not seem like a fuel issue. Thought must be an ignition issue. Checked all voltages on ignition system, all OK. Swapped out orange box ECU, no change. Swapped the coil, no change. Figured must be something in the distributor like the reluctor or pickup. Disconnected vacuum advance hose from the dist, revved it and ran OK. Hmm, bad vacuum can ?? Used a hand vacuum pump on the advance can, held vacuum just fine. Took of dist cap and noticed that the internal advance linkage had a very slight binding while pulling and releasing a vacuum with the hand pump. This slight binding was preventing the moving arm from the advance can from smooth movement through it's travel, thus really screwing up the timing on acceleration. A bit of lithium grease on the top of the arm and pin of the arm where it goes into the disc solved the problem.
