Im trying to figure out this problem on my small block.I put a timing light on it and its saying I have 45 degrees initial,so I turn the distributor back to get 20 and it wont stay running at all .
It's a newer MP distributor and a 6AL box,here is a list of things I did to try and figure this out.

Tried another timing light,same thing.

Zeroed the damper and checked top dead center,checked good.

Switched the pickup wires around ,It didn't make a diff either way?

Set the damper to 20 degrees and line up the rotor with 1 on the cap,and it won't start.If I turn it closer to eight it starts and runs .
Nothing has been changed,it's all the same stuff I had and never
had this problem before.
Just not sure what I'm missing
Thanks

You have to verify if damper slipped first. So find true top dead center.