Carburator emptying itself

[GTA_doum]

Hello,

I finished putting back my carburetor for '73 Olds 455 together.

This carburetor already had the problem of emptying itself overnight.  As suggested by the book, I did a pressure test, and no bubbles.  Even tried a heat test, then let it outside for the night, with fuel in the bowl and a white towel below it, to see if in the morning there would be any stain on it!  The towel was clean, but the bowl was half empty.  I guessed at that moment it just evaporated.
Anyhow, to be sure, I plugged the six caps on the carburetor with the Marine Tex epoxy, by putting a small drop over the caps.  I taught it would at least stay long enough, so I could determine if it is one of the plug leaking anyway.

After installing it back on the car, I started the motor and everything was working fine.  Let the car sit overnight, and in the morning, carburetor is empty again

Is it possible that only the heat of the motor is enough, that after few hours, the carburetor has evaporated all fuel in it?

Any suggestions would be welcome, as it is difficult starting this car first time in a day...

[akdale]

Let the engine sit over night.
In  the morning take the breather off, open the throttle, shine a flash light and see if the fuel is pooling in the intake.  That will tell you if it is leaking or evaporating.  Mine was wetting the intake.

[j_oetjens]

hello just a question do you have the filter in the carburetor it has a one way check valve in it that does not allow fuel to drain back to the tank I had that same problem after installing the problem was fixed

[GTA_doum]

Hello,
It's a filter that came with a kit I bought here.  Does not seem to have a check valve in it!  Since the carburetor already has a valve for this, it would be redundant system!

[Cliff Ruggles]

Did you pressure test the plugs at any point to see if they are actually leaking?

Pretty much a waste of time to wait for them to wet a towel under them.

If you suspect draining back, leave the clip off the needle.....Cliff

[GTA_doum]

Hello,
Yes, I did a pressure test with compressed air.  I even heated up the carburator to 90 celsius, put fuel in it, and let it sit for few hours.  There was no leak below it!

[Cliff Ruggles]

I've never seen one go empty that quickly.  I did some testing here with my own vehicle, carb still has fuel in it for 4-5 days, and getting really low by 7-8 days, just one or two good shots from the pump and it's empty. 

I can't imagine how one could evaporate all the fuel out in a few hours?......Cliff