Holley stumble trouble
Since the IFR controls fuel, and only fuel, increasing the IFR will, for a given pressure difference supply more fuel for the same air flow
and will continue to supply fuel at an airflow where it previously choked.
To keep the same air to fuel ratio but extend the flow to a larger throttle opening, increase both the IFR and the IAB. (edited: completed sentence)
In this instance I would suggest first changing the IFR. That alone will richen it.
If the AFR was good before, then likely increasing IFR will need to be matched with increasing IAB.
Choking happens to occur around 14"Hg. Whether this is why your carb is running out of fuel there or not or just chance, I don't know.
But this phenomenon is why tuning a idle system on an engine with low vacuum at idle is a bit more of a challenge than one with high vacuum at idle.
By choking I mean that increasing pressure difference doesn't result in any additional increase in mass flow of the fluid.
It's one of these situations
Because the inter-relationships are sensitive my general recommendation is that if its needs to be extended, do not richen.
Since the IFR controls fuel, and only fuel, increasing the IFR will, for a given pressure difference supply more fuel for the same air flow
and will continue to supply fuel at an airflow where it previously choked.
To keep the same air to fuel ratio but extend the flow to a larger throttle opening, increase both the IFR and the IAB. (edited: completed sentence)
In this instance I would suggest first changing the IFR. That alone will richen it.
If the AFR was good before, then likely increasing IFR will need to be matched with increasing IAB.
Choking happens to occur around 14"Hg. Whether this is why your carb is running out of fuel there or not or just chance, I don't know.
But this phenomenon is why tuning a idle system on an engine with low vacuum at idle is a bit more of a challenge than one with high vacuum at idle.
By choking I mean that increasing pressure difference doesn't result in any additional increase in mass flow of the fluid.
It's one of these situations