Hi Spud,
I know this is basic but just want to make sure. Been running a SM3 grounded to an oil pan stud on KB block with big red button kill switch. Recently bought someones spare SM-4 that you hopped up in 2008 with the big yellow capacitor on the outside. Since changing over, it seems the mag tries to fire sporadically with the switch off. Pulled the switch to see if contacts looked bad and they looked brand new, no evidence of arcing anywhere so I don't think the switch is bad. I see on the notes, at the bottom of the paperwork that you hand wrote to ground both heads to the coil, am assuming these grounds go to the yellow wire side of the coil, but just want to make double sure. I ran a Vertex for years because it only had 1 wire and even I could figure that one out.......lol. Thanks!!
BTW using 2-wire harness and 28900A redtop if that makes any difference.