MAB effect on main circuit

[GTO Geoff]

[1] This what Holley engineer Mike Urich said in the original. One of the most comprehensive books on carb function & tuning. He went on to become VP.
Page 23: ' The strong signal from the discharge nozzle is bled or reduced by the main air bleed so there is less effective pressure difference to cause fuel flow. The mixture will become leaner as the size as the size of the AB is increased. Decreasing the size of the AB increases the pressure drop across the main jet to pull more fuel through main system, giving as richer mixture.

[2] Carter Carburetors: ' As bleed size is enlarged, the vacuum [ depression ] required to initiate fuel flow is increased.

[3] Doug Roe Rochesterr carb book. p. 10. Same message as in the H book.

[Right hand drive]

[GTO Geoff]

You can type it out if you want to. It has no bearing on the OPs question which was: would a larger MAB delay the start of the main system & the answer is...yes.

[Right hand drive]

[CDN]

Got it Tks

[GTO Geoff]

RHD,
I don't need to type it out because it has no bearing on the OP's question. If you think it is so important you do it. if you do, it will show what I said.

I am not misinterpreting anything, you are. Carb function can be complex, but
this aspect of it's operation is simple physics. The larger the AB, the greater the 'leak' or reduction in signal strength at the booster, which then needs more air speed to generate enough signal [ depression ] to start pulling fuel. In short, a larger AB starts the system later & vice versa. Once flow starts, then things change & I agree with your comments.
Probably the best description of AB operation is described in John Passini's Weber book. He knew more about carbs than all of them. Larew's book uses the word 'assume' too many times.

[CDN]

Appreciate all the input good discussion
Do the MAB have that much impact on the cruise afr Am I focusing on the MAB too much or should I look elsewhere first
Will get time this Sat to make changes and watch the impact on my meter

Tks for all the feedback

[Right hand drive]

[CDN]

All good info
that was my plan IAB first but was not sure about the impact of the MAB

[GTO Geoff]

If you are running a PV in the primaries, you could try reducing the size of the main jet slightly & increasing the PVCR size to compensate, so that WOT mixture stays the same. As a test, you would only have to change the MJ size initially to see it it corrects the AFR.