Disappearing Fuel ???!!

[klassytin]

 I Recently acquired a '54 Manhattan Supercharged that had been sitting for years - likely decades.  The engine ran but extremely rough with lots of  black and blue  exhaust smoke.  I installed a new carb  kit and replaced the spark plugs, oil and filter  which helped immensely.  My issue now is that it won't start unless primed.  If I leave it for a day or two it needs an once or so of gas down the carb throat and then it starts instantly. It's fine when warmed up.  Any suggestions would be appreciated as it means removing the carb box for the supercharger every time I need to prime.  Thanks to all !

[pnw_oldmags]

Can you see the complete K on your rear hub caps??  My theory is rear end sag causes gas to back siphon to the tank and empty the fuel out of the carb / pump / and line back to the tank. 

Do you have any leakage ... fuel pump or carb of fuel? 

Solution - new rear springs or an electric fuel pump back by the tank after you fix any fuel seepage.

My thoughts.

[51Deluxe]

Check the adjustment of the automatic choke. Is it closed when cold? Does the accelerator pump squirt a healthy dose of fuel when you pump the pedal? That should work just like priming the carb if it's working right.

[retired wrench]

  Fuel pump may be leaking the fuel back to the tank.

[Fid]

Also, did you install a new accelerator pump diaphragm in the carb? Those get old and crumble which cause gas to leak down into the manifold and flood the car. Or, the fuel will leak out the bowl and evaporate.

[dpledger]

The gas in the carb bowl is what is supposed to provide for a cold start. Sounds like either the float level is set too low so there isn't sufficient fuel to provide a start or something is happening to the fuel that is in the bowl when the engine stops (leak as above.) If there were an issue of fuel getting from the bowl to the throat it should show up when the engine is running. Way to check this is before you try to start it see if the bowl is full. Take the plug off where the line comes in from the pump and pour a little gas down past the needle valve. If the bowl is full nothing will run in. If a significant amount runs in the bowl some has escaped. If it appears full, then you need to check if the level is correct. This likely requires taking the top section off the carb and inspecting.

[klassytin]

Appreciate all the suggestions.  The carb kit came from Willow Run and included a new accelerator pump so that should be functional. Also included was a new style needle and seat from "Daytona" which required modifying the float setting.  The new needle and seat requires minimal float travel which is supposed to improve the consistency of the air to fuel ratio from what I read in the instructions.  I will do some more investigating as suggested but am thinking a quality 6 volt electric pump might not be a bad idea.  Thanks once again

[joefrazer]

The needle and seat is the I issue. I installed a new kit in my 54 and used the Daytona unit and experienced the same problem. I swapped in the old needle and seat and my problem vanished.

[klassytin]

Thanks !! Good to know.  Maybe there should be an alert issued regarding the Daytona needle/seat?