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by David Zatz; most photos courtesy of auto parts seller DJD16
Chrysler Corporation’s Carl Breer worked with the Ball family, father and son, to build better carburetors; the benefits of their research went to any buyer of Ball & Ball carburetors. When the Ball family sold their company to Carter Carburetor in the late 1940s, their products were dubbed the Carter BB series (BB standing for Ball & Ball).
In the 1950s, two new carburetors were created based on that design, the Carter BBS and BBD series, essentially updated versions of the BB with single or dual “barrels.”
A carburetor barrel is a chamber where air rushes in, to hopefully mix with metered fuel; a venturi, or a narrowed area, increases the speed of the air and fuel. The two barrels can either work together, at once, or have “progressive” opening, where one barrel is used for most work, and a second one opens when needed. Most four barrels are progressive — they use two barrels most of the time, and open the others for hard acceleration — while the Carter BBD two-barrel had both barrels identically sized and opening at the same time.
Hemi Andersen noted that the main departure from the BB to BBD was using dual barrels; it also used metering rods rather than a fixed fuel metering jet to deal with all engine loads and speeds, except idle. The BBS came later, a single-barrel carburetor that took advantage of the BBD’s updates. Both were Chrysler standbys for many years, used on slant sixes (BBS) and small V8s (BBD).
For the 1977 Volare and Aspen, Carter adapted the BBD to the Slant Six. The new BBD-8087 was created mainly by cutting down its size so the smaller engines wouldn’t get too much fuel at once and “bog.”
In the same year, the 318’s BBD gained a mixture adjustment for higher altitudes, which could be set from the top of the carburetor; this was only used on cars sold in high-altitude areas, and was replaced in 1982 by a separate mechanism.
These photos make it clear that the BBD had identically sized barrels and venturis. You can see the white plastic adjustment caps on the two screws that controlled the “idle mixture” — the amount of fuel that was mixed with air on idle.
The other two screws, seen in the above photo on the left, controlled the engine idle speed when the engine was warm and cold. They were screwed in or out to rest on a cam, which moved as the engine warmed up. The cam was hooked up to a mechanical thermometer, that is, a strip made of two metals that expanded differently as they were heated. That caused the metal to bend more or less, pulling the cam; but the cam would only move when the screw was not resting on it, so the driver would press the gas (so the screw would move up, letting the cam turn), start the car, wait a few moments for it to warm a little, then press the gas lightly (to let the cam turn back a little), and start driving. As the driver pressed the gas, the cam could turn again until the engine was warm, and finally the second screw rested against a flat part of the cam — that was the warm idle speed. These are best shown in the black and white “Super Six” carburetor illustrations above.
In 1979, the BBD used on the slant six was made “tamper proof” by concealing the idle mixture screws, using a plug during the final factory adjustment. Dealers would have to remove the plugs, change the mixture, and, though many probably skipped this step, replace the plugs. This replaced the earlier idle mixture limiters.
The final Chrysler use of Carter BBD carburetors was in the 1984 cars. For 1985, Chrysler switched to Holley — but only because Carter had stopped making carburetors.
The various Carter serious, except some of the later four-barrels, still have a strong reputation for reliability and durability today.
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Chrysler 1904-2018 •
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