Set timing, hei mod

Hi!

I have a valiant with 5.2 magnum engine.
Running megasquirt for fuel only.

I have mopar electronic distributor with the HEI mod done and msd blaster 2 coil.
I set initial timing at 8 btdc, but runs really bad. Sounds to be feeling good around 15-18 btdc. Is this normal after the mod?

engine is basically stock. Just thin head gaskets, kegger mod and headers, exhaust.

best regards//Will from Sweden.