Holley 1920 Help needed

Lucky you have a good Holley 1920. I went thru many long ago before I got a good one. If yours looks like airgrabber's photo (pre-smog, i.e. no big vent tube off the bowl), then your bowl vent should be open at idle (rubber disk at bottom of photo, i.e. top of carb). As mentioned, bend the rod to make that true. I also agree that your float is probably not shutting off fully, so the left-over pressure in the fuel line causes slight flow into the bowl until it overflows. It is easy to remove the inlet fitting and needle and inspect or replace.

There were 2 other 1-bbl carbs for the slant that I know of. The Carter BBS was on early engines. It is very similar to the ubiquitous 2-bbl BBD that came on most 318 engines. You can find manuals free on-line (I did). The Holley 1945 was later. Some people love those. In general, Carter's are simple and robust but Holley's work better when they aren't ****ed up. I think there was a Holley Economaster version for the slant in the 80's for better mileage, but sounds like you want power.