pics please of your holley 1920 set up and linkage

That spring in my pix is the throttle return spring, so you can ignore that; like I said, this is on a '62 dart (B body) and the linkage is different.

I never found out for sure but I suspect that the needle valve rubber was worn or cracked on my carb (it was 52 years old!), and letting in a little gas all the time, even when the float was trying to close it. The float was not gas-soaked (I weighed it to be sure), but I replaced it anyway.

It would not hurt to time it to around 2-3 degrees BTDC at idle.

A rebuild with a new float would be in order for your carb. Mike's Carburators sells the 12.7 oz floats.

Do you have the list number off of your carb? It will be 4 digits (and maybe a letter); it may be preceeded by an 'R'. It is probably located on the flat area beside the fast idle screw and cam in my carb's pix (the center, sidways pix....).