Carter BB-1 updraft carburetors

[carbking]

Doing research on Carter BB-1 updraft carburetors.

 

There have been quite a few threads here about folks having issues with BB-1 carbs on larger engines. I have posted a few times that we have had issues with customers trying to use these on engines over maybe 275 CID.

 

So, more information:

 

It has been assumed by many, including me, that the 289s (or 289sd) was the largest of the BB-1 updraft carbs. It is the largest of the universal BB-1 carbs. But the 871s and 2075s carbs used by Chevrolet on the 235 and 261 engines have venturii with a 25 percent larger area than the 289s/sd. The largest engine which used the BB-1 as original equipment was the Chevrolet 261.

 

The 261 was rated at 3400 RPM, so one could surmise that MAYBE one of these larger BB-1's MIGHT support early engines of 450 or so CFM if the engine redlined at 1500~1600 RPM. But one would still need to address the idle circuit.

 

The idle jet in the Chevrolet carburetor is 0.031 inch, whereas the idle jet in the 289s is only 0.0236.

 

Thus even using the larger Chevrolet carburetor would require the idle jet to be enlarged if used on engines of more than 261 CID.

 

As I have custody of the Carter prints, I have been able to do the "paper" research, but now need some "physical evidence".

 

If anyone has any Carter BB-1 updrafts he/she would consider selling or trading, please see my list of wanted BB-1's in the parts wanted section. Just want one of each. At my age, no intent on trying to buy more carburetors for inventory. These will be disassembled, casting numbers placed in my database (to help folks in the future identify carbs missing tags), restored for pictures, and sold. Again, only one of each required, and we currently have 11 different. These numbers do not appear in the wanted list. Do not wish to acquire more of those I already have.

 

Jon

[Akstraw]

Jon,

These are very popular carbs, and your work will be a valuable contribution to our hobby.  I have two, and will check out the numbers this week.

Andrew

[carbking]

Thanks Andrew - yes, they ARE popular, probably more popular than they should be. The folks in the Great American Race discovered them early in the history of the race, and thus began the race to see who could buy them up before their neighbor did  

 

They work VERY well on smaller engines, and they are very compact (unlike the better Stromberg and Zenith universals).

 

My biggest objection to the BB-1 is the mechanical accelerator pump. I know everyone here knows that one does NOT pump the footfeed on any vehicle with an updraft carburetor; but not all of our heirs are aware of that fact. Once the starting procedule is complete, the BB-1 is as good as the equivilent Stromberg or Zenith.

 

I have been keeping casting number databases on Carter carburetors, including the BB-1, for decades. Just not happy with the small amount of data in the BB-1 database. There are 46 different, and I only have 11, less than 25 percent. I am closer to 75 percent on the WCFB, AFB, YH, and UT; about 95 percent on the W-1's.

 

Jon

Edited January 21 by carbking (see edit history)

[Chris Bamford]

33 minutes ago, carbking said:

...I know everyone here knows that one does NOT pump the footfeed on any vehicle with an updraft carburetor; but not all of our heirs are aware of that fact...

Count me as one here who DIDN'T know that, and I'm not even an heir 🙂. I've run a BB1 (unknown model) on my 373 in3, 1,500 rpm max, 1912 KisselKar 4-50 since 1997. The car has always started and run well by my standards, although I have little basis for direct comparison. My standard practice is to give a quick pump or two when starting from cold; starting from warm I generally open the throttle fully, retard the spark fully and hit the starter for quick results.

 

I for one am very interested in how to better start and run the car with this carb and why pumping the footfeed is not recommended. Photos below in case there is anything specific to my unit worthy of comment.

 

I apologize if my post and request is divergent to the topic at hand, and would gladly start another thread or take it off-forum. Thank you Jon for doing this research and for being so willing to collect and share your deep and valuable expertise. 

 

 

[dodge28]

I used a BB1 on my 1928  225 Dodge engine. It was rebuilt by a professional Carb rebuilder. I could never get the idle screw to work. Fully screwed in or out made no difference. According to Dodge the original  carb was a UX something , I cannot remember. NO BODY IN THE DODGE BRROTHERS WORLD KNEW HOW TO HOOK UP THE LEVER.  I went to carter BB1. It needed an adapter to mount. Later I was advised to use a Carter BBsa something I cannot remember the number now. The mounting bolts on the manifold were too wide so I made a new adapter. The carb works. But  the air idle  screw has no effect on fine tuning.  

[carbking]

Chris - if one has a downdraft carburetor and one pumps the footfeed, fuel runs into the intake manifold (gravity), vaporizes, and helps start the vehicle.

 

If one has an updraft carburetor WITH a mechanical accelerator pump (the Carter BB-1), and pumps the footfeed, fuel runs into the lower section of the carburetor throttle area, and if pumped 3 or 4 times for sufficient volume, runs out of the air inlet drain down (gravity) on to whatever is directly below the drain. The drain on your carburetor is plugged with a bolt??? The drain should be functional. On marine carbs, Carter would install a "drip loop", connecting the drain with a vacuum source above the throttle plate. This is very simply a loop in some copper tubing. The fuel that drains down from the intake when the engine is shut off, drains into the drip loop, where it sits harmlessly until the next time the engine is cranked. The vacuum created when cranking the engine pulls any fuel still in the drip loop into the intake.

 

If one has an updraft carburetor with a vacuum accelerator pump (Stromberg SF/SFM series, Zenith 63/263 series) and pumps the footfeed, one merely exercises one's ankle  The vacuum accelerator pump does nothing until the engine is running, and has vacuum available to charge the pump spring for subsequent action.

 

One should start an engine with an updraft carburetor by using the choke (if the carburetor has one).

 

Your carburetor is one of three possible models, which you can determine by measuring the center to center of the mounting bolt pattern:

 

2 3/8 or 2 7/16 - 245SD

2 11/16 - BB1D

2 15/16 - 289SD

 

If you ever need a rebuilding kit, the identification will be the first question asked you.

 

Jon

[carbking]

18 minutes ago, dodge28 said:

I used a BB1 on my 1928  225 Dodge engine. It was rebuilt by a professional Carb rebuilder. I could never get the idle screw to work. Fully screwed in or out made no difference. According to Dodge the original  carb was a UX something , I cannot remember. NO BODY IN THE DODGE BRROTHERS WORLD KNEW HOW TO HOOK UP THE LEVER.  I went to carter BB1. It needed an adapter to mount. Later I was advised to use a Carter BBsa something I cannot remember the number now. The mounting bolts on the manifold were too wide so I made a new adapter. The carb works. But  the air idle  screw has no effect on fine tuning.  

 

GUESSING!

 

Based on your post, you have a Senior Six.

 

The early production 1928 Senior Six used a Stromberg TX-2, which was found to be too small. Sometime early on in production (I don't have a serial number break), the TX-2 was replaced with the UX-3. The intake manifold and the UX-3 would have 2 15/16 center to center bolt spacing. Carter recommended the 289s carburetor with a tapered throttle bore, and a 1 1/16 inch venturi. Since your bolt spacing on the manifold was too wide, it is probable that you do NOT have the 289s, rather probably a BB1A or BB1D with 2 11/16 bolt spacing, a cylindrical throttle bore (not tapered) and a 1 inch venturi. The mismatch of airflow from carburetor to intake manifold is probably messing with the idle signal, causing the idle screw to not function correctly. The engine would also be slightly down on power because of the smaller carburetor venturi.

 

Even if rebuilt by a professional, the wrong carb will not function correctly.

 

Jon

Edited January 21 by carbking (see edit history)

[Chris Bamford]

1 hour ago, carbking said:

 

Your carburetor is one of three possible models, which you can determine by measuring the center to center of the mounting bolt pattern:

 

2 3/8 or 2 7/16 - 245SD

2 11/16 - BB1D

2 15/16 - 289SD

Thank you Jon, that is very helpful and of course makes perfect sense. 
 

My carb is 2-11/16 across the bolt centres, so a BB1D model. 
 

It would seem from your initial comments that this unit is a little small for my 373 in3 engine. Is that a reasonable assumption?

 

I max out around 50 mph which is 1,500 rpm in OD.  Comfortable open road speed is 45 in OD. 

[dodge28]

Jon, thank you for the info. The bolt pattern on my Senior manifold is 2 11/16. The manual says the carb for this engine is a UX2. There are other makes and models suggested as you mentioned. Not naming any specific. There is a picture in the manual showing a UX3 for my Senior.  The bolt mount pattern for the UX-3 is way out. I had one of those and I gave it to my Ausie  friend .I sent a BB1D to him also. He has a 28 DB Senior. So I gave him the UX2 ,the Ux3 and the BB1D. The most recent BB1D is the last pull off from my car. In all I estimate I may have spent near 25 hundred dollars in trying to get a decent carb.  My next move will be to get an adapter to convert to a downdraft carb. In the present carb BB1AS, and the previous  BB1D, the IAS screw never worked.  Do you remember the bad pot metal of those carbs ?

[carbking]

Apparently, there was an early and a late intake manifold. Remember the manuals were printed prior to production of the vehicles; and of course would not show mid-year changes, the service bulletins show those.

 

There is no mention in the Stromberg records of a UX-2 for the Senior 6. Not arguing the point, simply looking at the Stromberg records.

 

Stromberg did release the UX-2 for the Standard Six and the Victory Six.

 

I don't have the date when the TX-2 (2 11/6) was changed to the UX-3 (2 15/16), but these are the units listed as correct for the Senior Six application.

 

Decades ago, when we acquired the remains of Stromberg including the remaining factory inventory, we submitted a sample of that pot metal to a metalurgist, who suggested the failure was due to an excessive amount of lead in the early zinc alloy. Not just carburetors: door handles, distributor bases, all of it up to the early 1930's had problems.

 

Before you convert to the downdraft carb:

 

The BB-1 carburetor has TWO idle tubes, one quite obvious, and the other hidden in the lower casting. Most idle issues with the BB-1 (assuming the correct carburetor) are caused by failure to remove the hidden idle tube and blowing out the passage. Try that before doing the conversion.

 

And I would suggest looking for the larger Senior Six manifold, so a larger carb could be installed.

 

EDIT: more information. The TX-2 used by the Senior Six had a venturi of 1 3/32 inch; and it was replaced by the UX-3 with a venturi of 1 1/8 inch. The BB1A and BB1D both have a 1 inch venturi. So the TX-2 is 20 percent larger than the BB1A/D and the UX-3 is 27 percent larger in venturii area.

 

Jon

Edited January 22 by carbking (see edit history)

[dodge28]

Jon, thank you. I admire your capacity for retaining all that information and sharing it with us. .  I hope you live a hundred years and more. I will  be 88 on March 9 coming.

Cheers . Have a nice day Jon.

[stakeside]

13 hours ago, carbking said:

Apparently, there was an early and a late intake manifold. Remember the manuals were printed prior to production of the vehicles; and of course would not show mid-year changes, the service bulletins show those.

 

There is no mention in the Stromberg records of a UX-2 for the Senior 6. Not arguing the point, simply looking at the Stromberg records.

 

Stromberg did release the UX-2 for the Standard Six and the Victory Six.

 

I don't have the date when the TX-2 (2 11/6) was changed to the UX-3 (2 15/16), but these are the units listed as correct for the Senior Six application.

 

Decades ago, when we acquired the remains of Stromberg including the remaining factory inventory, we submitted a sample of that pot metal to a metalurgist, who suggested the failure was due to an excessive amount of lead in the early zinc alloy. Not just carburetors: door handles, distributor bases, all of it up to the early 1930's had problems.

 

Before you convert to the downdraft carb:

 

The BB-1 carburetor has TWO idle tubes, one quite obvious, and the other hidden in the lower casting. Most idle issues with the BB-1 (assuming the correct carburetor) are caused by failure to remove the hidden idle tube and blowing out the passage. Try that before doing the conversion.

 

And I would suggest looking for the larger Senior Six manifold, so a larger carb could be installed.

 

EDIT: more information. The TX-2 used by the Senior Six had a venturi of 1 3/32 inch; and it was replaced by the UX-3 with a venturi of 1 1/8 inch. The BB1A and BB1D both have a 1 inch venturi. So the TX-2 is 20 percent larger than the BB1A/D and the UX-3 is 27 percent larger in venturii area.

 

Jon

 

I purchased a BB1 carb and believe it to be a much later version than the original 1929 one. It never would work on my 1929 DA6. I had the original Steward carb rebuilt and it runs great.

 

 

 

[carbking]

The throttle shaft and fast idle link indicate one of the universal BB-1's.

 

C to C 

 

2-7/16 - 245s (cast bowl), 245sd (diecast bowl)

2 11/16 - BB1A (cast bowl) BB1D (diecast bowl)

2 15/16 - 289s (cast bowl) 289sd (diecast bowl)

 

The original Stewart was and is an excellent carburetor.

 

Jon

[dodge28]

Jon, thank you. I admire your capacity for retaining all that information and sharing it with us. .  I hope you live a hundred years and more. I will  be 88 on March 9 coming.

Cheers . Have a nice day Jon.

[alsfarms]

I second the idea that Jon is a great resource and we are all benefited as he is willing to share his knowledge with us.

Al

[carbking]

My wanted ads for these carburetors are doing nothing!

 

I have added 3 more to the 11 different I had, making 14 different, but I found these on a bottom shelf in my own inventory.

 

Since I have custody of many of the remaining Carter files, empirical research is relatively easy. But I NEED physical carburetors to take my research to the next level.

 

Below is a table comparing the sizes, both S.A.E. flange size, and internal venturi sizes of all of the BB-1 carbs.

 

Please note the largest internal venturi is 1.1875 ( 1 3/16 ) inch. These were primarily used on the Chevrolet 235 CID stovebolt 6.

 

The 2075s will flow the most of any of the BB-1's. It has the same internal venturi as the 871s series (used on the Chevy 235), however the internal portion of the throttle body was tapered, giving somewhat more flow. The 2075s was used on the Chevrolet 261 engine.

 

The Carter BB-1 is a good carburetor, hundreds, perhaps thousands of enthusiasts have proved this; but a carburetor that originally was used on a 261 CID is not going to work well on a 500 CID engine! And while it may work on a 285 CID, probably not as well as a Stromberg or Zenith with the correct air flow.

 

I NEED CARBS! The list needed is in my "wanted" ad.

 

Condition is relatively unimportant, as long as the carb is complete, and the original tag is in good shape. After 50 years of fixing junk sent to me, I am pretty good about fixing junk!  

 

So, throwing our some bait  

 

Jon

 

Edited February 10 by carbking (see edit history)

[alsfarms]

It is great that you are willing to share knowledge about carbs......we are a dying breed I fear.

Al