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For what it's worth, I had a very similar issue on my 39 Six with a Carter WA1.

Have you checked the integrity of the carb float? If the float has a hole and is sinking, the effective fill level will be higher than it should be. THe float is low, so the needle valve is open, pouring more fuel into the bowl. When the engine is running, it may not be noticed, especially if the idle speed and mixture have been recently adjusted, which may compensate and mask the issue. When the engine is shut down, the residual fuel line pressure between pump(s) and carb will just pour into the bowl and over the idle level port and right down into the hot manifold. The height relationship between float level and idle port flow circuit is critical.

Further, the car may be able to be restarted if done within a minute or so of shutdown, or once the car has time to clear the flood.

Before I determined that the issue was a sinking float, I checked the anti percolator function, other carb flow circuits, the idle, and all kinds of other things. Once repaired, all issues resolved.

It is possible to make solder repairs to a carb float, but I recommend having a pro do that unless you are skilled at low heat soldering. You don't want to change the weight of the float with globs of solder as it will affect the bowl fill level.

Hope this helps.
Pat

For a Q&D/diagnostics fix:
"T" in a valve on the SUCTION side of the pump with a tall verticle snokel. BEFORE turning off the engine, open the valve and let the engine run the gas out of the bowl.

I've never used such a valve and there mite be electricaly actuated valves to make it easier to to open/close the valve from interior of car.

OTherwise, u're in for alot of work that MAYBE will not solve the problem if it is something unforseen yet. Ez enuf to dod and mite buy u some time while trying other easier ideas than seperating manifolds, rebuilding carbs for 2nd and 3rd time, etc .etc.

The easiest thing to try first is run the car with no hood on it. See if there is any improvement.

Again, thanks for all the advise! I am trying them all. As for the float, it was dry when I rebuilt the carb a couple of months ago so I do not think is has a hole.

If the float was sinking and the bowl filling up, you would think that the easiest way out for the fuel excess would be the vent. The fact that I got a spray of fuel would suggest that the trapped fuel was under pressure which might suggest that the fuel was coming from the accelerator pump?

If the fuel was caused by say a vapor bubble in the fuel line to the carb, again I would think the fuel would have been released through the vent not the venturi? I will try the brick on the accelerator pedal suggestion!

I checked the carb at least three times during the test drive and I had no overflow problems until I arrived home. The car has to pull a pretty good grade getting to the house and I had to turn on the elect pump to keep from vapor locking the last 1/4 mile. So, the problem might have something to do with the pressured fuel line when I shut the car down?

Thanks again for all your support,

Rod

" I had to turn on the elect pump to keep from vapor locking the last 1/4 mile"

Did the engine just try to quit running or did it make a rather shallow kind of pup - pup - pup -pup sound????

If it made the pup-pup-pup sound then it might be a lean running condition in addition to the vapour lock. Otherwise it's just a vapour lock condition.

The engine just started to stumble and the extra pressure from the elect pump settled it right down. I found that I have a gallon or two of diesel fuel in my barn so will give the tank a shot of diesel fuel this afternoon and will do another test drive. Still hot here with change of dry lightning this afternoon. Not good for our very dry conditions!

Rod

Rod, try a 5% mixture of diesel fuel to your gasoline. That should do it. I have heard of folks using up to a 10% mixture. With a 10% mixture you may start to get odor and smoking. This does not happen with a 5% mixture, at least not in my experience. Nasty little problem you have there, I hope the diesel fixes it.

(o[]o)

I put in about 5% diesel yesterday and went for a drive. The thunder storms in the area cooled things down so I do not know if it worked or not. I do know that I did not have to use the elect pump on the road up to my house which is better then the day before.

Rod

Pleased to hear you had a good experience. Maybe you have fixed it, let's hope so.

(o[]o)

update! I replaced the "new needle valve" on the float with the original one after soaking it and the seat in carb cleaner for a week. It appears to be doing a better job then the "new needle valve" that came with the carb kit. The old needle valve is all metal and pointed. The new valve was flat with a elastomer insert and the seat was ridged to press into the elastomer.

I think the car is running better with the old valve! I have solved the vapor lock problem with the electric fuel pump. I took the car on about a 50 mile round trip this weekend and it performed well except I did capture some gaso in the pan I put under the carb so everything is not 100% but I am getting closer.

Tried the diesel fuel in the gaso. Waste of diesel and time. The vapor lock problem was about same but the electric fuel pump took care of the problem.

Thanks for all your help and suggestions. I am getting closer and will let you know if I find the solution.

Rod