Carburator Fuel "leak down" problem

A customer of mine has a new MP six pack on his 440.

If he leaves the car sit for a week or so, the carbs seem to empty themselves out only leaving enough fuel to MAYBE fire once. Then you crank and crank and crank and crank and crank and nothing happens...

You remove the shaker bubble PITA, and pour gas down and she fires right up and works perfectly fine with all the float bowls adjusted and working properly...

Let it sit again and it's the same process all over again...

What would cause the fuel system to empty out like that ?

It's most likely evaporating not draining. Modern gas is crappola. EXTREMELY common problem these days.

Yeah..you almost need an electric fuel pump to keep from cranking the engine so much.

little mallory pump out back by the tank.. sure saves a lot of cranking! dan

Alan,
This is a common problem on 440-6 and 340-6 Holley 2300's. I have the same issue on my T/A.
If it sits for more than 3 or 4 days, I have to crank before it fires.

I had a problem with the fuel pump rod on a BB. Not hardened and it was wearing out on the cam side.

If the car has not stalled when driving then it is more likly the bowls have emptied when sitting.

been dealing with this on a 440+6 since 85 when I bought it. would love to hear some solutions for when I get it back together.

I also think its evaporation since I pretty much have that problem with all my cars, some worse than others maybe depending on engine cranking speed and fuel pump condition.

I have the same problem on all my Mopars with AFB, Holley 2300 & 1920, Carter BBD.
There is one exception, I have a slant six I run a Holley 2300 500 on, it can sit 4 weeks, pump it twice and it will fire immediately. I have no answer to why the gas doesn't evaporate out of this carb.

i've been wondering, if the "pre-lube" oil set up, that holds some oil under pressure, to pre-lube a high performance motor, could be plumbed into the fuel system? would store a bit of gas under pressure (4-6 psi) and could be used to refill the carb(s) after sitting a while? with the new carbs being aluminum instead of zinc, and gas being corrupted with alcohol, something needs to change. it's sure not going to get any better, if the damned corn growers have their way.

heat from manifold is boiling the fuel away? hot gas evaporates faster the cold gas, also i think they formulate the gas that way to sell more. it is very bad. we used to run cam-2 purple in the race car and it would evaporate each week, went to cam-2 blue and never had the problem again, different evaporate rates.

Buried in my notes for initial 440-6 startup is to fill the float bowl via the vent tube until you can see the pump spray

I have a '64, and '65 Barracuda with Commando 273's, and a '69 Roadrunner with a 383 and have that problem all the time when they sit for more then 4 or 5 days or more. When I go to start any of them I don't even set the choke until I let it crank for a bit to pump the gas up to the carb.