BBD reference page?

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Bugman said:
1974 and up bbd solid fuel design main metering system. 1973 and back air bled main metering system. Two completely different systems. Theory of operation and part style and numbering systems. In the solid fuel type carburetor circuit timing is affected by the actual level of fuel in the bowl. High fuel level main system activates early, low fuel level main system activates late. In Air bleed carburetors actual operating air fuel ratio is sensitive to the level of fuel in the bowl
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Bugman said:
This thread has a picture of an air bleed blohttps://www.slantsix.org/forum/viewtopic.php?f=19&t=63460&hilit=bbd+jets&start=30od BBD Emulsion well well
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solid fuel no well tubes

solid fuel.jpg


green vdots.jpg
 
Second picture air enters the main system very close to the Top by those green dots
 
From what I've Been Told the older air bleed system Jets were flow tested in cc's and then given a part number. Rather than rely on a hole size. Back in the day Carter part numbers weren't that much of a problem, real parts stores real counter people Carter books behind the counter.
 
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Thank you, that explains A LOT!

I figured the jet number equated to a size like your example, but it made no sense that 1 step lean would be a lower number than 2 steps.

BTW where did you get the chart with the 120-310S jet info.
 
Think of how a jet is made. Widest part at top, that takes more room in main hole, nest step on rod is smaller, less taking of hole and more gas, you get the last step.
 
mocarJoe said:
Think of how a jet is made. Widest part at top, that takes more room in main hole, nest step on rod is smaller, less taking of hole and more gas, you get the last step
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I think we are talking two different things. I get the steps on the rods.

Jet has home that has a cross section area of 1 ( just numbers here) then you put a rod down the center with a cross section area of 0.5, effective cross section area of the combo is 0.5.

The next step the cross section area of the rod is 0.25 so effective combined cross section area is 0.75 etc.

I was saying that in the FSM they call out main jets that are 120-310s then if you want to lean out the carb "one-step" you use jet number 120-294s and if you want to go one more "step" lean you go to jet number 120-297s
 
Dana67Dart said:
I think we are talking two different things. I get the steps on the rods.

Jet has home that has a cross section area of 1 ( just numbers here) then you put a rod down the center with a cross section area of 0.5, effective cross section area of the combo is 0.5.

The next step the cross section area of the rod is 0.25 so effective combined cross section area is 0.75 etc.

I was saying that in the FSM they call out main jets that are 120-310s then if you want to lean out the carb "one-step" you use jet number 120-294s and if you want to go one more "step" lean you go to jet number 120-297s
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Inkedcarter cat_LI.jpg
 
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