Need Quick Fuel carb tuning assistance
Be sure its not the fuel pump. When you let up on the throttle while cruising, some of fuel pumps have a spring that's too stiff and sends the pressure over 7 psi.
That will overfill the bowls. You can guess how I learned this. :rolleyes:
Second. The specs in your first post dont show the IFR. Everything else being equal, smaller IFR will usually get noticibly leaner idle and engine braking.
71 IAB is on the smaller side. Changing IAB is more of the fine tune compared to changes in IFR. Larger IAB usually will lean out the idle circuit - more noticibly on the top. Say you made a big jump to 78 IABs. Then I would expect to experience stalling as you add throttle to go up a hill at 25 - 30 mph, maybe 2000 rpm. Expect is the key word. Sometimes changes don't go the direction we expect. We're dealing with fluid dynamics. Bleed in too much air, or change the mixture velocity from laminar to turbulent flow and suddenly relationships seem wacky.
As far as IFRs high or low. I generally like low but feel free to stay with high unless you have a problem that seems to be inconsistant.
Thinking more about it more, with the downlegs, the big thing may be not to bleed in too much air too early. If testing these I'd start with smaller top e-bleed, like .026 instead of .028"
Probably first experiment with after feeling comfortable with fuel level/pressure is primary IABs. Make that one change and no other.
Vizard is a great writer. His info is pretty good.
But be careful. If you are not careful, sometimes trying to follow him will take you down a rabbit hole.
Mine was a long and somewhat expensive journey.
Eventually I learned what was real, what was applicable to the situations/carbs I was working with, and therefore my mistakes were a part of learning.
But it all started with trying to do some of the things suggested in Vizard's How to Build Horsepower V2
No carb should, but OOTB not that surprising to me.
Be sure its not the fuel pump. When you let up on the throttle while cruising, some of fuel pumps have a spring that's too stiff and sends the pressure over 7 psi.
That will overfill the bowls. You can guess how I learned this. :rolleyes:
Second. The specs in your first post dont show the IFR. Everything else being equal, smaller IFR will usually get noticibly leaner idle and engine braking.
71 IAB is on the smaller side. Changing IAB is more of the fine tune compared to changes in IFR. Larger IAB usually will lean out the idle circuit - more noticibly on the top. Say you made a big jump to 78 IABs. Then I would expect to experience stalling as you add throttle to go up a hill at 25 - 30 mph, maybe 2000 rpm. Expect is the key word. Sometimes changes don't go the direction we expect. We're dealing with fluid dynamics. Bleed in too much air, or change the mixture velocity from laminar to turbulent flow and suddenly relationships seem wacky.
As far as IFRs high or low. I generally like low but feel free to stay with high unless you have a problem that seems to be inconsistant.
Thinking more about it more, with the downlegs, the big thing may be not to bleed in too much air too early. If testing these I'd start with smaller top e-bleed, like .026 instead of .028"
Probably first experiment with after feeling comfortable with fuel level/pressure is primary IABs. Make that one change and no other.
Vizard is a great writer. His info is pretty good.
But be careful. If you are not careful, sometimes trying to follow him will take you down a rabbit hole.
Mine was a long and somewhat expensive journey.
Eventually I learned what was real, what was applicable to the situations/carbs I was working with, and therefore my mistakes were a part of learning.
But it all started with trying to do some of the things suggested in Vizard's How to Build Horsepower V2
