RE: Velocity Stack on the 35 gasser ??
John,
As you noticed already, only a small amount of fuel is thrown out from the carburettor.
This tends to be more noticeable at part throttle settings...
There is a certain number of crankshaft degrees, that while the crankshaft rotary valve is open, the piston is descending, raising the crankcase pressure beyond atmospheric.
When this pressure change happens at high engine speed, the inertia of the air coming into the carburettor and running through the crankshaft, will keep the flow in the correct direction, i.e. into the engine.
But when this happens at mid-low engine speeds, the flow is actually reversed and mixture is expelled through the carburettor, taking some more fuel with it, as it flows out.
This creates a small 'cloud' of fuel-vapor close to the carburettor entrance.
For this, an extended intake 'trumpet' will offer a full solution, as that cloud is contained within the trumpet and not thrown, by the prop-wash, all over your plane. It is then sucked back into the engine by the engine's next induction.
You will have to close the low-speed needle a noticeable amount, to compensate for the lost fuel that no longer is.