I went up and set the carb on it, to give an idea. Here's where the vac advance is plugged into. It must work, it was screaming up the road, when I gave it throttle. I dunno?

Can't imagine what would provoke a claim that these are "junk carbs" or that the car is "supposed to" have a Holley 1920. Neither is a correct guess.

For future reference, applicable carb tag number is 3840s. Floats may be obsolete from some or all of the superficial catalogues, but they're still easy to get. Usually not needed; they don't tend to fail.

This what's plugged with a screw is the vacuum balance port. Some carbs have it and others don't. That screw isn't supposed to be there; remove it and hope the screw hasn't enlarged the hole.

(it's not a distributor vacuum advance fitting, that's on the other side of the carburetor, protruding from the middle (not lower) casting. The red arrow pointing to where the distributor is hooked up is, in fact, the distributor vacuum advance port.)

This carb, like most of them this age, will need more than just a clean-and-gasket-kit job; looks like it's overdue for the throttle body to be rebushed. That takes a specialist or an expensive special tool not worth purchasing if you're not going into business.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dannnnn!! I wondered when you were gonna show up!!
Okay tag number... 3840s. Thank you!
Okay, so remove the screw, and just leave the hole "open"? Just making sure I understand. This won't be a vac leak then??
I did spray the shaft when i had it running, the motor never changed. I hope my shaft is fine. Seems tight.
Okay, I feel a little better now!

Nope, no original hole in a BBS there per FSM illustrations. Interestign point above, I never heard of that. That point is right above the throttle plate opposite to the idle ports but this level would give an oddball 'sorta ported' vacuum. Needs to be plugged...not much chance it is not wallowed out now.... IMO.

Saw a similar extra hole in a Holley 1920 thread recently too.....must be some sort of disease, or a sub-shadetree 'fix' applied when the carb is too rich.

JB weld the hole shut?

The hole belongs there.

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Joshua

Pics in service manual are generic, not specific enough to transform an uninformed guess into sound advice.* The hole is supposed to be there. It was not put there by a shadetree mechanic. It was put there at the carburetor factory. Yes, it's really supposed to be open to the atmosphere. Changing the size of the hole or selectively plugging it is into the realm of advanced carburetor tweaking and tuning, not a good idea to wade into until the basic carb is in as close as possible to perfect unmodified working order.

*Ohhhhhhh yeah…now I remember why y'all don't see much of me on here any more.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Okay, leave the hole there, and hopefully it is not larger than factory hole was...?? I won't know though if the hole is the right size after removing the screw?

I never checked exactly, but it's meant to be about 3/32" diameter or so. If it's been clawed up by the screw threads, it's been enlarged.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I'll try to check it the best I can. I don't really know a way of shrinking the hole. That I can think of anyhow.
I already ordered my carb kit, so I want to try and make this carb work. It does run, just crappy and very rich. It needs a good rebuilt, it is filthy!

Dan is correct. I have carter fuel systems service training school book from that era. Vacuum balance vapor relief hole. Its part of carb venting system. The rest of the venting system was designed to work with that hole open.Depending on carb application etc holes may be there or not. If hole is there it should be left open. That hole is above closed throttle plate so no vacuum leak.

Okay, this may sound stupid, but...If the hole is en larged too much. Can I plug it off, and drill the correct size hole next to it?

If the hole has been enlarged you can epoxy the hole closed and then drill it to the proper size. Or plug it with lead shot and drill that.

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Joshua

Thanks! Would you happen to know what size drill bit I should buy?
I know what epoxy is like JB weld, but don't know what lead shot is?

I just measured mine. 0.105 so 3/32 0.097 or 7/64 0.109