I have a 4k in a sierra and i'm trying to sort out the advance.
Not sure if this is normal or not but.
With the advance vaccuum line on the advance port(i think) the dizzy will go from 8deg down to 0deg for just less than a second then it will come back up past 8 deg and up to whatever..
I havn't tested with a timing light but with it on the manifold it still seems to happen
The carb has literally nothing else attached, no emissions or anything
only things connected are choke cable, accel cable and advance line, every other port is blocked off.
Also this is only testing while sitting in the driveway under no load.