I have the same tach/dwell meter my family's had since the 1970s. I remember setting dwell angle through the little access door in the distributor, but I haven't owned a car with points since 1990.That could be. It's been a very long time since I had my '85 Blazer. Back in the day that's what we had to do. Either way, the idle mixture and idle will have to be adjusted.