How to set timing for initial start up on new build?

67Dart273 said
It is "not quite" correct

The rotor only selects the cylinder, it does not "set" the timing.

If you are running points, once you get the rotor "on" the no1 cylinder, move the distributor retarded, then advance until the points open. Use a test lamp, etc

If you are running breakerless, set the distributor so the reluctor is in the center of the core. This is not 100% accurate

Once you "get the hang" of this you can actually turn on the ignition power, move the dist "retarded" and then "move" it towards advanced until you generate a spark. Do this back and forth several times, trying to slow down rotating your distributor, and stop the rotation right at the spark point. With practice, you can get this within a few degrees

ALSO you can set initial timing "on the starter" while cranking

If you set the crank at 40* BTDC and turn the rotor so you have taken up the advance, and line up the rotor with the number 1 post, that's exactly (or pretty dam close) where it should be.

OP, it needs at the very minimum the total timing on it you think it will run at. I never, ever start a fresh engine with OE geometry with less than 40 on it. They start better and don't generate a bunch of heat in the exhaust.