My '66 Barracuda has a 225 and TorqueFlite. Being a California car since birth, it was originally equipped with the Cleaner Air Package.

The service manual suggests it should have a Holley 1920 carb but I suspect it's currently a Carter, as (though there's no tag on to be found) the side of the bowl is marked "Ball and Ball made for Chrysler Corporation" and 6-1695 is cast on one side.

The service manual also suggests this carb is for the 170.

Would I be better off with the Holley?

Does the Cleaner Air Package mean anything in terms of carb selection? Does anyone actually still have a working CAP and/or can explain its purpose??

I suspect a vacuum leak or a carb rebuild is in order, as the car starts well and idles well, once warm, but hates to accelerate. It feels like the distributor does not advance, but I have tested the vacuum pot successfully.

Advice cordially welcomed.

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'66 Barracuda

The Cleaner Air Package is simply a closed crank case ventilation system (oil filler breather cap has a hose connected to air cleaner) combined with a special carb and distributor. The special carb and dizzy provide more emissions control by limiting advance and fuel consumption given various vacuum signals.

The purpose is to restrict emissions to pass California state law. Sounds like you may have a Carter BBS which would have likely been standard on a 170, but probably performs just fine on your 225. My '66 Dart (California) had a reman Carter BBS installed when I bought it.

These days I have a new-old-stock Carter BBS and it does just fine, I don't think its under carbureted but then again I've never tried a good Holley 1920.

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'66 Dodge Dart

The answer is "either". There is a long-persistent misunderstanding that the 170 engines got small Carter BBSs and the 225s got big Holley 1920s. That's wrong. There were Carter BBS and Holley 1920 carburetors in a larger-than-most-realise range of sizes, specified and installed as original equipment for just about every permutation (170/225, auto/manual, with/without closed crankcase vent, with/without clean air package, with/without taxi/fleet package, with/without air conditioning) from 1962 to 1969. Which one got installed on any particular car depended on nothing more or less than what was at hand in that production plant during that shift on that day when that engine was put together. For the first couple years of CAP production (which started in '66), mostly Holley 1920s were factory-installed on CAP-equipped slant-6s (170 and 225 alike). As CAP production expanded, Carters were added into the mix. Some applications, such as the 1970 and '71 198 slant-6s, all of which were CAP-equipped, used only Carter BBSs.

Your current carburetor is a Carter BBS. It and the Holley 1920 have various relative merits and drawbacks, but at this late date it is far more important to have a carburetor in as good condition as possible than to have any particular brand and model of carburetor. It has grown very difficult to get good carburetors; the supply of new ones is smaller every day and "remanufactured" ones are garbage.
At the factory when the car was being built, yes. In your driveway as you're trying to make the car run well, no.
All California cars starting in '66 and all 50-state cars starting in '68 got the CAP, so...yes.
Its purpose was to reduce the amount of unburned hydrocarbons and carbon monoxide in the engine exhaust. The early CAP consisted of a carburetor jetted leaner than they usually were at that time, and with less than the usual carburetor-to-carburetor variation in calibration and flow; a distributor with modified advance curves, a specification calling for retarded base timing (5° ATDC, compared to 2½° BTDC for regular engines at that time), in some applications a distributor vacuum advance control valve, and upgraded radiator and radiator fan to deal with the hotter running caused by the leaner jetting and retarded base timing.

The system worked well when properly adjusted.

The vacuum advance control valve has three vacuum nipples: a large one to manifold vacuum, a small one to the vacuum advance port on the carburetor, and a small one to the distributor vacuum advance. If you pop off the plastic cap, you'll see there's a spring underneath and a slotted screw running thru the center of the spring to adjust the tension.

What this valve does is advance the timing under closed-throttle, high-vacuum situations (i.e., deceleration or coasting with your foot off the accelerator). The way it works is simple: as long as the vacuum signal from the manifold vacuum port is equal or less than that from the spark advance port, the distributor vacuum advance receives an ordinary ported vacuum signal as though the valve weren't there at all. When the throttle is closed, the spark advance port is above the closed throttle plate, so it produces no vacuum signal. But manifold vacuum is very strong under the closed throttle plate above idle speed; this strong manifold vacuum overcomes the valve's spring tension and manifold vacuum is sent to the distributor vacuum advance. This advances the timing. Why? Because with closed-throttle coasting or deceleration, you've got a relatively rich, slow-burning mixture headed into the cylinders; you're hauling fuel through the idle circuit of the carb with the ultra-strong manifold vacuum, but because the throttle plate is closed, you haven't got much air coming in. Advancing the spark under those conditions gives more time for the mixture to burn, thus reducing emissions. It also increases fuel economy. It also reduces engine oil contamination. It does not take any bite out of performance or driveability, nor does it have any other detrimental effect.

The valve must be adjusted properly; if the spring tension is too loose you'll get vacuum advance action at idle (by manifold vacuum overcoming the too-loose spring). That will louse up your ability to set the idle mixture and speed for a smooth, stable, clean idle. If the spring tension is set too tight it'll be as if the valve isn't there at all.

Read more here (Popular Mechanics November '63 discussion and test of the prototype CAP) and here (1967 Chrysler Master Technician Service Conference booklet on the system with detailed explanation of the distributor control valve —*keep reading onward; starting on page 10 are the check-and-adjust procedures for the valve).

Note that you can turn this piece of hardware to your advantage by advancing the base timing from the retarded CAP spec. Try a base timing setting of 2½° BTDC at 750 rpm with the hose pulled off the vacuum advance and plugged.
Probably a faulty accelerator pump. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

The carburetor may be too far gone to resurrect with a simple rebuild kit -- that happens. If that turns out to be the case, then it'll be time to consider a new carburetor if you can find one, or having your carburetor professionally refurbished (again, not a "remanufactured" unit!).

If your '66 happens to have air conditioning, and therefore the cable rather than rod style throttle hookup, it'll be much easier for you to find a good new carburetor.

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

Nope, that's the fully-closed crankcase ventilation system. It was installed on all California cars starting in '64 and all 50-state/Canada cars starting in '68. It is not a part of the CAP.
Nope, the CAP distributor has a longer advance curve -- not shorter.
The CAP was not designed to control or alter fuel consumption.
This myth refuses to die.

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

Actually if you quoted my full sentence you might have realized that I took it nearly word-for-word from the FSM... "... combined with a special carb and distributor."
Wait, didn't you just say CAP consisted of leaner jetting? I may be wrong but it would seem like a change in jets would alter fuel consumption.
Probably because the FSM plainly states that the BBS was primarily used on the 170. Don't get me wrong, I trust Dan on the details but its not like we have access to your intimate knowledge of production line practices. So the myth is perpetuated by folks that oddly trust a car manual published by the manufacturer.

Dan, we love your knowledge and advice, but would love to see a little grace now and then.

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'66 Dodge Dart

Yes.
The CAP was not designed or intended to control or change fuel consumption. Leaner jet giveth, bigger radiator fan and retarded base timing taketh away.
Find me the page in the FSM that states "The BBS is primarily used on the 170". Tear it out and hand it to me and I'll eat it—without ketchup!

The factory parts catalogues go into much greater detail on what carburetors were specified and used on which applications.

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

At the risk of walking into a minefield, the reason I was first concerned is that the service manual for 66 appears to specify the 170 used the Ball and Ball.

Section 14, page 13:

The Standard Ball and Ball single throat carburetor models BBS-4099S and BBS-4100S are used on the 170 cu in engine when the vehicles are equipped with a manual or automatic transmission respectively. The BBS-4103S and BBS-4104S are used as above but with air conditioning...

The Special (Cleaner Air Package) Ball and Ball single throat carburetor models BBS-4101S and BBS-4102S are used on the 170 cu in engine when equipped with manual or automatic...respectively.

Section 14, page 5:

The Standard Holley carburetor models R-3271A and R-3279A are used on the 225 cu in engine when equipped with manual transmission. R-3275A... with air conditioning. Holley models R-3272A and R-3280A are used on the 225 when equipped with automatic. R-3276A with air conditioning.

Special (CAP) Holley carburetors R-3273A and R-3281A are used on the 225 engine when equipped with manual; R-3277A as above but with air conditioning. Models R-3274A and R-3282A are used on 225 engines when equipped with automatic. R-3277A is used as above, with air conditioning.

These sections prompted my original question. I appear to have a different carburetor than was originally installed by the factory, if the service manual is to be believed.

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'66 Barracuda

Service manual incompleteness is annoyingly common. The '66 parts catalogue lists Carter BBSs and Holley 1920s for most equipment variants of the 170 and the 225.

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