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What is the the adjustment of lower valve for the BB-1 updraft carb. Is this a metering jet that can be adjusted for engine based on it’s size. My DA6 is 208 cu in. 

The adjustment on the top one is 1 1/4 turns.

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If it is like the Zenith's and is main jet start at 3 to 4 turns out . Set idle at,  you have . If it runs , rev and hold half to two thirds rpm . Then clockwise in until rpms start to drop off . Then back counter-cw until max rpm reached . going past you notice drop off and roughness again . Back at max point turn 1/4 turn ccw out to rich it .

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  • 2 weeks later...
  • 3 months later...

Still have problems with the Carter BB1. I get engine to fire up using spark retard, 1/4 throttle lever and closed choke. After it fires I fully advance the spark and the engine dies. As I increase the throttle I hear a starving for air sound. Upper screw is set at 1 1/4 turns and lower main metering jet is set at 4 turns open. In the previous diagram the metering jet is part of the fuel supply for staring the car.

After many attempts I did get it idle but it’s to unpredictable.

Any suggestions are appreciated.

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How are you setting timing . If you get running at all adjust that first . You'll need a good ear or vacuum gage to do both . Both need rto be revisited as you get closer to optimum .

  Vacuum adjusting does better job compensating for lash and wear in distributor .

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Idle needle was of incorrect type on my overhauled BB-1 and the car would regularly miss at idle, stumble and stop if not giver choke or throttle. With correct needle it idles perfectly. I have also experienced another "overhauled" carb that missed an internal balancing spring and gave far too much fuel pr throttle. Otherwise is false air the most common problem, and make sure the ignition is perfect as stated i the adjustment sheet.

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Here is a link to my website with the original Carter service literature.

 

http://www.thecarburetorshop.com/Service_Carter_BB_updraft.pdf

 

I think your adjustments may be off.

 

Suggested INITIAL setting of the idle mixture screw (top) is 1 turn. Functional range 1/4 turn to 1 1/2 turns.

 

Suggested INITIAL setting of the high speed adjustment is 2 1/2 turns. Functional range 1/2 to 5 turns.

 

Jon.

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 I realize that the condition of the engine will effect the starting also. I am attempting to repurpose an older engine that was given to me.

The greatest effect is the condition of the rings. Even through the compression was uniformly low at 65psi the rings may not seal easily. It takes a lot of cranking to get an oil seal between the walls and the piston. The problem is compounded further by unburnt fuel in the cylinders.

By using your suggested settings Jon I have got it to idle and accelerate . Thanks for your support.

Next I will tackle the Steward vacuum tank. Getting closer to the road.

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I would not call that compression low .  50-55 at cranking speed and 65 at 450 rpm for trucks is list in prior years mechanics manual .Remember these are low compression engines . May want to check fuel also . Are you using non-ethanol or older fuel ?

   Glad it coming along .     Tom  

 

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  • 1 year later...

Good day
I have a question about the AFR values.
I have a 1930 Desoto SA Sedan Six with Carter BB1. What AFR values are at idle and what values are at full throttle. When I measure I have at idle afr 15 and full open trottle afr 14.5. in my opinion this is too lean. the main metering screw I have then turned completely out. What are the options for setting it richer? thanks and best regards Daniel

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On 4/2/2021 at 5:42 PM, keiser31 said:

Don't know if any of this will help you....

BB1.jpg

BB!-2.jpg

BB13.jpg

BB14.jpg

 

Hello Keiser31 thank you very much, this is very helpful. do you know how much compression this engine should have? i have +- 87psi at all cylinders (Desoto 1930 SA Sedan Engine Six Series) Thanks and Best Regards

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1 minute ago, DanRen said:

Hello Keiser31 thank you very much, this is very helpful. do you know how much compression this engine should have? i have +- 87psi at all cylinders (Desoto 1930 SA Sedan Engine Six Series) Thanks and Best Regards

Not sure about what compression it should be.

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