Carburetor (Secondary Well)

[Charles Reese]

Excuse my ignorance but what is the purpose of (i.e. how important is.. ) the Zenith brass ‘secondary well’…. my double venturi style does not have one (no threads in hole)… my single venturi has the threaded hole but is missing the brass insert … both seem to run properly. If I need to put the brass insert in, is the repro item (brattons) a reasonable alternative? What size tap would I use to ‘chase’ the treads (mild rust) in the hole?