318 Engine stumble

Well the most likely causes are the 4 possible causes I listed. Some may add to that list. I don't think it is a big problem.... just maybe new.

Moving the distributor rotor back a tooth will not fix this particular problem.

Checking these are pretty self-explanatory. You may need to find some pix to compare your distributor for where the reluctor should point. Or post a pix of the top of the shaft with the rotor removed and the reluctor points and pickup visible so others can compare to theirs.

I am assuming what you have for pickup so bear with me:
Look at the pickup coil riding on the plate that the vacuum advance can move. There should be a thin gap visible on the surface that faces the reluctor teeth and perhaps a mark on top to match that gap's location.

Look to see if, when the rotor is very close to pointing at spark tower, that one of the pointy teeth on the reluctor is pointing exactly at that gap on the pickup.

Based on what seems to be going on:

• If it is lined up that way, then the likely problem is the pickup leads to the ignition module are reversed. That is the last of the 4 problems listed.
• If it is not, then any of the 1st 3 problems are possible causes.

I have not looked through the thread to catch all of the details of the ignition setup, beyond the fact that it is an HEI system. So I may be missing something. But it looks like the rotor position and the reluctor/pickup position are quite misaligned from where they should be. If they were aligned properly, then your technique of lining up the rotor as a rough initial setting would work as before.