The Carter BB-1 carburetor - information

[carbking]

There seems to be much mis-understanding of this really good carburetor and its applications.

The BB-1 carburetor SERIES was designed and tested in 1930 and 1931 by Carter, and released for production in the fall of 1931 for use on 1932 Plymouth, DeSoto, and Chrysler automobiles. At this time, the BB-1 was really leading edge technology. As a side note, the fall of 1931 was a really good time for carburetors, as the Stromberg SF SERIES was released for production at the same time.

Mechanics of the day were quick to realize the quality of the BB-1 and began substituting these units for use on older vehicles with older technology carburetors.

As the above was brought to the attention of Carter, Carter immediately tested and released three different universal model BB-1 carburetors which were much better suited for replacement use than the O.E. units mentioned above.

These three replacement units were:

S.A.E. size 1 - Carter 245s

S.A.E. size 2 - Carter BB-1A

S.A.E. size 3 - Carter 289s

S.A.E. size 4 - Carter 263s (prototypes, testing, but NO PRODUCTION)

The universal carbs featured: (A) "universal" throttle shafts that extended through the casting on both sides to facilitate fastening the clamp-type throttle arm on either side, ( adjustable main metering jet to aid in calibration without having to buy several different sizes of main metering jet, © a "fast idle" provision, which amounted to a flat rod connecting the choke and throttle which would slightly open the throttle for additional RPM when the choke was engaged, (D) different (richer) idle jets and main air bleeds to facilitate the use on different sized engines.

The pre-WWII castings were both cast iron.

History kind of intervened or the Carter BB-1 might have been used on lots of different cars; but the mechanical fuel pump was becoming more common, thus the proliferation of downdraft rather than updraft carburetors. So the only original automobile applications for the Carter BB-1 were the aforementioned 1932 Plymouth, DeSoto, and Chrysler units.

However, the Carter BB-1 still had uses. Cab-over-engine (COE) trucks continued to use updraft carburetors, as did marine applications due to the reduced engine height required. So the Carter BB-1 in all three physical and several different internal sizes was used on truck and marine applications well into the 1960's. The most common applications were Chevrolet and Dodge trucks, and Gray and Owens marine. There were also some military and industrial applications. In all, there were 69 different carburetors released in the BB-1 series.

Note that the "service" requirements for truck and marine applications is quite different than for automobile. These engines are basically asked to idle, and to run at some constant higher RPM, thus the internal calibration of carburetors for these units often does not have the same circuitry for part throttle and changing RPM as is required for smooth operations in an automobile.

The BB-1 castings were redesigned after WWII, with a zinc alloy replacing cast iron for the lower (bowl) casting. As the zinc alloy will warp without fastenings which are much closer together (reference the Rochester B series carbs), Carter changed both castings to have 6 bolt-to-throttle body screws rather than the three used with both castings being iron. The universal carbs were then renumbered as follows:

S.A.E. size 1 - 245s -> 245sd

S.A.E. size 2 - BB-1A -> BB-1D

S.A.E. size 3 - 289s -> 289sd

The Carter BB-1 does have several "issues", all of which are easy to address by a competant rebuilder:

(1) During periods of long disuse, the brass accelerator pump will stick to the lower body, often making disassembly difficult. The use of an ultrasonic cleaner, virtually always will free the stuck pump, and allow disassembly.

(2) The idle circuit has a "hidden" jet, deep in the lower casting which requires the use of a special screwdriver to remove. The orifice is quite small, and failure to remove the jet, and clean the passageway beneath the jet will generally result in poor idle quality.

(3) The power jet has a replacable spring, which fatigues due to having to support the power jet pushrod. The spring MUST be replaced during rebuilding. Failure to do so will cause the power jet to always be open, resulting in an overrich condition throughout the RPM range. The spring comes in the better rebuilding kits, and is easy to replace, but it must be done.

The only complaint I have with the Carter BB-1 series carbs is the mechanical accelerator pump. MOST other updraft carburetors with accelerator pump activate the pump using vacuum rather than the throttle.

So why is this important?

If a novice attempts to start an automobile with an updraft carburetor and pumps the footfeed a dozen times as he/she would do with a downdraft carburetor, the mechanical accelerator pump will pump fuel into the throat of the carb, but since the fuel must travel UP into the intake, the fuel instead runs out the front of air intake onto whatever is below the carburetor (sometimes the exhaust!).

However, if the same novice uses the same procedure with a carburetor with a vacuum activated accelerator pump, he/she merely exercises their ankle! The pump does not function until the engine is started and vacuum is present.

Vehicles with updraft carburetors SHOULD be started using the choke valve.

As to identification, ALL Carter BB-1 carburetors were originally tagged. If the tag is gone, exact identification requires the carb to be disassembled, and the jets and air bleeds compared against the original prints. Due to the popularity of the BB-1 and the universe full of Chevrolet truck carbs versus the very few universals, this creates problems for the user.

If information is necessary on S.A.E. sizes, please refer to this link:

http://www.thecarburetorshop.com/Carbshop_carbsizesandCFM.htm

Jon.

Edited February 20, 2015 by carbking (see edit history)

[keiser31]

Thanks for sharing!

[Dave Henderson]

If anyone is interested, I have a cosmoline packaged rebuild kit that I believe is for a military truck Carter B&B carburetor, likely of WW!! vintage. PM me.

[hchris]

Most enlightening, thanks for going to the trouble of sharing this information; mind if I copy it to a newsletter down here ?

[carbking]

Most enlightening, thanks for going to the trouble of sharing this information; mind if I copy it to a newsletter down here ?

No problem, feel free to quote anything I post which you feel is worthy of quoting, and thank you for the complement.

Jon.

[lozrocks]

Excellent information. But I believe the carburetor was not designed by Carter. Carter took control of Ball & Ball Carburetors in 1929 and continued to produce the Ball & Ball basic designs of which the BB1 is one. Carter made some improvements to design and patented the new design in 1930. There are examples of the B&B1 dated as early as 1928.