OK, figured out the prob here. Took the dist. cap off and tried moving rotor by hand. Rotor had close to 90 deg. of play! I realized that it had to be losing timing because the rotor was jumping around. So I pulled the dizzy, but it looked OK. Then I dropped the (externally mounted) oil pump to see if there was something broken in the slot that drives the dist. Turns out what turns the tang on the bottom of the dist. shaft (thereby driving the distributor) is 4 thin pieces of sheet metal that fit into slots on the end of the oil pump shaft. These were quite bent, so while the oil pump would still turn the dist., there was some slip-sliding going on; i.e. when the tang on the dist. would slip against the drive pieces of sheet metal, it would throw the rotor off by probably 60-80 degrees and thus kill the timing. I don't know exactly what the best way to cure this problem would be- I straightened out the little pieces of sheetmetal, but I'm worried that eventually they'll just bend again and maybe even break? Maybe I'll replace them with something more stout. Thanks for the reply, Arnswine.
