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On the EE-16 the float chamber vent with the opening starting just under the air cleaner area appears to be connecting to the float chamber via a vertical passage. It sounds like it may be similar to what O_D describes with other EE models needing a baffle arrangement to prevent any fuel from being thrown out the vent opening by centrifugal force or whatever. Could a similar arrangement be missing on the carb in question?

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I checked the vent and it is open and clean. The carb seems to be perfect in every respect. But obviously I've missed that something which makes it spew gas at high speed.
Thanks for your help,
I've learned a bit.
Bob

O_D mentioned part of a gasket as forming a baffle. If the illustration is accurate I could see a need for something at the rear half of the chamber to keep acceleration or maybe even a turn from sending the fuel to the rear and then sloshing up the vertical tube. Without some sort of baffle, if fuel is thrown to the rear of the chamber and covers the vertical tube then that movement plus incoming fuel being admitted to replenish the chamber at the same time could easily push fuel up and out. In the illustration there is sort of a white line across the chamber roughly on top of the float which could represent the gasket between the top and bottom. If that gasket were solid over a portion of the rear half of the chamber that would serve as a baffle. Perhaps someone familiar with the carb can better describe the baffle and what to look for.

Pushing fuel out the vent makes complete sense now. It only occurs during high speed when the fuel pump is pumping at a maximum. I'll try lowering the float a bit and see what happens.

Wish me luck,
Bob

The fuel pump is pumping at its maximum well before high engine speed, the volume of fuel it can pump is a multiple of the fuel need of the carb. Adjust the float level and float drop according to manufacturers specs. Scientifically derived information beats guessing.

This is an interesting problem. I can't envision any kind of motion from driving that could force fuel that far uphill to the vent outlet. Also I'd bet the farm that lowering the float level from its proper specification will NOT solve it and will just create other issues.

Perhaps it is time to check the fuel pump pressure. Perhaps the pressure is high enough that when the needle opens a spray shoots across to the base of the vent stack, a portion of it having enough energy got climb the stack. I know, sounds pretty far-fetched but....

I'm not sure what to do now. Put back the same way I found it, and look for a different solution, like what?
Any clue would be appreciated.
It's a rebuilt fuel pump.
Doesn't the pump run at the same speed as the engine pumping more at high speed than at idle?
Bob

Well, of course the pump mechanics cycle in direct correspondence with engine rpm, but the actual fuel delivery is determined by the float drop which in turn is related to fuel demand.

Fuel pump output pressure is determined by the spring inside the pump which is pushing down on the diaphragm as the fuel is admitted to the carb. In some cases excess pressure is caused by the stretch of the diaphragm. If the pump was assembled with the diaphragm essentially flat with minimal ability to flex, the tension can cause increased pressure as well as cause a shortened life on the diaphragm. It is most important to move the arm as if it were on the engine and the diaphragm be at full stroke before tightening the screws holding the halves together.

If that air vent passage is small, conceivably some fuel could be forced up and out if the mass in the chamber hit the opening with enough momentum some fuel was forced inside.. Similar in principle to how water can be made to run uphill a short distance by using a small diameter conduit for the inclined section fed by confined pressure from a larger diameter conduit. Of course the flow is considerably reduced but the Romans put the principle to good use in getting fresh water delivered by the aqueducts redistributed around the city and particularly to villas of the wealthy up on the hills. If there are air bubbles separating droplets of fuel that could be another method of fuel flowing up the passage. Surface tension keeping droplets intact and each time the mass of fuel hit the opening it could push a drop out followed by another air bubble and another droplet. Again, it would take a narrow passage so it all depends on how big that air vent is.

It wouldn't take more than a few drops to wet the top of the carb. From the description of everything being dry while the car is still no matter the engine revs, to me that motion scenario seems to be plausible. One other possibility is fuel coming out from a defective fitting or a casting issue. An owner of a 47 had the issue but I will have to go back thru some emails to remember the exact cause. IIRC, he found vibration was opening the defect allowing the leak since he had a dry carb otherwise.

I don't know exactly where the opening is located but is there a possibility of wrapping or taping a small section of cloth over the vent opening. Nothing heavy that would totally close it but just a layer or two to absorb moisture. Drive the car and then stop and immediately pull the cloth off for examination. If it is damp it would seem fuel is coming out the opening and if dry, it is time to look elsewhere.

I'll try the cotton swab on the vent opening. You are correct there isn't much gas, but I can smell it when driving on the interstate at speed, and of course when stopped.
The car is down for awhile awaiting a new solenoid for the starter. As soon as it's running again I'll post the results.
Bob