There is a direct correlation between gap and dwell. If you get the gap right the dwell will be right. I've seen people use the flap from the cardboard carton that the new points came in as a feeler gauge. One thing to note, if you adjust the points to the correct gap and then tighten the clamp screw, the gap will change. You have to learn how much it changes then initially set the gap off by that much so it will be correct after you clamp it down. Always check after you tighten the screw.
