After completing tune-up from points to plugs the dart is ticking over very nicely. been driving for a few days and realized I made a classic rookie mistake and forgot to reattach the vacuum advance hose to the distributor.
(Though the car is running fine without)

So of course I connect the line and the idle drops a small amount (which I believe is expected?) but the car then runs quite rough and has what appears to be a bad off-idle miss again and accellerates roughly.

I removed the line once again, and have been driving fine for a few days but I want to address this now and don't quite know where to begin.

Anyone else experienced this before?

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Franklyn
1965 Dart GT - 1949 Plymouth Special Deluxe

Where is the other end of the vacuum advance hose going to? Intake? Carb? What port on the carb?

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Casually looking for a Clifford hyperpak intake for cheap.

going to carb yes.
to one of the ports,
the other port is plugged with a piece of hose and a screw.

you can see where the lhose goes to on the carb and you can also see the plugged secondary port on the carb in this photo:

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Franklyn
1965 Dart GT - 1949 Plymouth Special Deluxe

Since the air cleaner blocks a view of the carb, I am going to ASSUME that you have one of the later 1920 carbs that have a cannister purge port on the passenger side towards the front of the carb. I am going to assume this because (a) you clearly no longer have the original rod-style throttle linkage carb and (b) earlier 1920 carbs didn't have two vacuum ports on the passenger side that could be mixed up. See HERE. EDIT- Except for the anti-carb icing system Dan mentions below. That added another fitting.

Based on this ASSUMPTION, I will posit that the distributor vacuum advance hose is currently incorrectly connected to the charcoal canister purge port on the carb. I believe the port that is plugged with the hose and screw is actually the correct distributor vacuum advance port. The best way to tell is to get a vacuum gauge and find the port that has no vacuum at idle but gets full manifold vacuum upon the opening of the throttle.

I recommend you plug the hose back into the vacuum advance on the distributor (but check and make sure the vacuum advance pod still holds a vacuum first) and plug the other end of the hose into the correct port on the carb and leave the canister purge port uncapped.

I also recommend you get rid of that clear plastic fuel filter and replace it with a metal one, do the fuel line mod, swap to HEI electronic ignition, get a "closed" air cleaner and rig up a cold air intake, and upgrade to a dual chamber brake master cylinder. I can't tell, but if you haven't already, it is a good idea to upgrade to an electronic voltage regulator for the alternator rather than the original mechanical style your car was built with. A dual-field alternator is nice too.

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Casually looking for a Clifford hyperpak intake for cheap.

I may add a small point to Reed's excellent answer: The engine's performance is not influenced much by the vacuum pod. The pod primarily gives additional timing advance in a situation like high speed cruising on a freeway, thereby improving your fuel economy. In the FAQ in the engine section, there are links to discussions related to adjustment of the vacuum pods.

Olaf.

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Aspenized

Your vacuum advance is connected to the correct port on the carb. The plugged one is for the carburetor anti-ice system, see here, which was standard equipment on Canadian but not American slant-6s in '65. It looks as if someone swapped on a Canadian carb (or some other mix of components with no provisions for the anti-ice system), so they simply plugged it off at the carb. This may be related to your odd idle findings; those carbs are calibrated to account for the extra air at idle from the anti-ice system. With that plugged off, the idle speed screw would have to be turned inward to open the throttle plate more than intended to attain the right idle speed, which would uncover the vacuum advance port, giving advance vacuum at idle (which there shouldn't be). This would tend to cause the idle speed to increase(!) slightly when attaching the advance hose, unless the distributor timing is advanced just to the borderline of too far, in which case adding vacuum advance will push it over the edge into poor running. I had that situation on my own '65 years ago; it ran fine without the vacuum advance connected, but skipped and missed (especially in Neutral at higher-than-normal idle speed) with the advance connected.

Things to check:

1. What is your base timing setting? And are you sure the timing mark is accurately pointing to TDC? The outer ring of the crank pulley, which has the timing mark on it, can slip relative to the hub. Then any given timing reading understates the actual amount of advance.

2. Does your air cleaner baseplate have a small nipple on its underside?

Once we know the answers, the path to fixing it will be pretty straightforward.

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

Wow, Dan must have X-ray vision. He must see something I can't. Any chance we can get a non-blurry photo of the passenger side of the carb without an air cleaner on the carb?

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Casually looking for a Clifford hyperpak intake for cheap.

Going off the placement of that capped-off vacuum line. If it were a canister purge port it would be at the right front corner.

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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 thought the capped off port was the correct ported vacuum source for the distributor but the vacuum line for the distributor was actually connected to the charcoal canister port on the front right of the carb. Dan knows more about the finer points of slant six carbs than I do, so I will yield to his expertise. However, a clear picture of the carb would still be helpful.

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Casually looking for a Clifford hyperpak intake for cheap.

Well, you could certainly be right — especially now I look again and see the car no longer has the rotating-rod throttle linkage. So yeah, a pic of the carb without the air cleaner will clear it up.

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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 to think he should use the capped off line. Seems I remember my 1920 carb having the port there.

Hey Guys,
thanks for the thoughts,
I found a moment to take a pic with the air cleaner off to get a better view.
there does seem to be two ports, but they seem equal as far as front or rear. Any ideas after seeing the picture? Is my vaccuum advance on the wrong port?

It's an Autoline C-641 Carb and you can see in the photo the two ports, one plugged with a screw and one with the vaccum advanced hose whcih is currently disconnected at the distributor end (due to the aforementioned drivability issues) .

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Franklyn
1965 Dart GT - 1949 Plymouth Special Deluxe

ALSO,

I must say, you guys are great! and I'm pleased to have found this community of such knowledgable folks. Thanks muchly for the discussion and advice. I have learned so much here already in the first month or so of owning a slant though find myself going to bed later and later to finish off reading some past thread of interest


My air cleaner DOES have a small nipple on it's underside that is not currently being used.

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Franklyn
1965 Dart GT - 1949 Plymouth Special Deluxe

Ah! OK- looks like it is a Carter BBS (in need of rebuilding if all the gunk on the outside is an indicator of how much it is leaking), NOT a Holley 1920 as I initially ASSUMED.

With that clarification and looking at your new pictures, I will change my diagnosis. The vacuum advance hose appears to be hooked to the correct port. I believe the port with the hose and bolt might be the anti-icing system Dan was referring to.

Going back to your original symptoms- is the hose plugged down by the distributor or is it open? Have you verified that the vacuum advance pod on the distributor holds a vacuum and doesn't leak?

EDIT: You know, at this point I recommend you get a different carburetor. The one you have is showing obvious signs of leaking, and there is a high likelihood that it is a carb intended for use with the anti-icing system Dan has referred to. If you don't have the rest of that system, or aren't going to hook it back up, then I recommend you get a later Holley 1920 cabruretor and use it instead.

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Casually looking for a Clifford hyperpak intake for cheap.

Your pic bears out my original post; that's a carb equipped for the Canadian-market anti-ice system. Your vacuum advance is hooked up correctly.

Did you check the base timing, the timing mark accuracy, and look for a nipple on the underside of your air cleaner yet?

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