My 340 getting 6 mpg
I see the ignorance of Newbomb Turk rises to the top in post #107 like cream rising to the top.
Larger main air bleeds will
lean the mixture, not richen it. Same dope blames the carb he has on the dyno because he does not have the jetting parts on hand to jet it. It's the carb's fault!
As I said earlier in this thread, I believe the carb being used has some fundamental internal problem & a different carb should be tried if possible.
Below on air bleed function is from the Holley book, by Holley Engineer Mike Urich
View attachment 1716245710
I've already proven you a liar. I can do it again.
I explained it above, like it works in the real world. I'll say it a different way. I doubt that will help you but someone else may learn.
Because of the position of the MAB and the fact that the MAB is connected to the main well and the nozzle, at low air flow rates the main air bleeds functions as an emulsion jet. And it behaves in that manner until the nozzle is activated. And what activates the nozzle (booster)?
As the airspeed increases and the fuel starts to flow from the nozzle, the MAB now acts like an air bleed and starts to do what it's name says it is. It starts to bleed off flow from the booster.
The MAB is needed because the booster can deliver more fuel than the engine needs. You wouldn't use the same emulsion and MAB for a straight booster as you would with a down leg booster or the same emulsion with annular boosters.
You are trimming the fuel with the MAB at high air flows.
If you were to look at it on a graph, assuming that the emulsion is correct and such, you'd see that a .034 MAB would have a different curve than say an .026 MAB.
The difference would be the bigger MAB will tilt the curve rich at low air flow and tilt the curve lean at high air flows.
The smaller MAB will tilt the curve LEAN at low air flows (because the smaller bleed, acting like an emulsion bleed isn't adding as much air to the main well and the fuel in the main well) so the booster starts later (making it leaner at low air flows) and at higher air flows (the booster has started) it will tilt the curve rich because its not bleeding off as much signal.
It's pretty simple really unless you don't think for yourself. Bewy thinks that because the MAB reduces the signal to the booster, making the curve tilt lean at higher air flows that it must do the same at low air flows.
It doesn't. It works exactly as I outlined above. It's easy to see with O2 sensors on the dyno.
What I can't explain is why some of the carbs come with huge MAB's in them, other than they have so much emulsion they are trying to kill more signal to keep the fuel curve half assed close.
Always remember, at low air flows the MAB acts like an emulsion jet which is adding air, which makes the fuel in the main well lighter, which causes that fuel to flow to the nozzle (booster).
Big air bleeds and too much emulsion have caused as much grief as setting power valve timing at half idle vacuum. Another Bewy tuning error.
As for the junk **** edeljunk carb on the dyno, it was over 16:1 with the stock jets and rods. I have a full Carter strip kit and he had some loose jets and rods but neither of us had rich enough jets and small enough rods to get enough fuel in it to make a pull.
I don't tune junk that is a power loser.
