I have a 57 T-Bird with a 4150 Holley 4 brl carb. This is the same carb that was on it new. It has started this issue about 5 moths after overhauling the carb. It starts great, has good throttle response and runs nice and smooth. Just like it always did. The issue: after sitting for lets say 2 to 3 days, at takes a good while to start because the fuel in the carb has drained out. IE the carb is dry. It does not leak on the outside so I assume it is draining into the engine. I thought maybe the power valve, but a new one did not fix the issue. Any ideas? Thanks Beep
I suspect the Power Valve is blown . It will allow fuel bowl to empty into the intake . Easy way to check it is , idle mixture screws adjustment , if no change when adjusting the screws , power Valve is out to lunch Sent from my iPhone using H.A.M.B.
I had a 57 Fairlane that did the same thing. I put a wooden spacer under the carb, replaced the float, changed the power valve, replaced the needle and seat. Bought a new replacement Holley. Problem cured. I had that old carb apart about a half dozen times. Try filling it up and setting it on the bench level and see if it drains setting there.
Does that carb have the lever operated bowl vents, If so it could be that the vent is open when the car is parked . Modern fuel evaporates much faster than 50s fuel this style of carb was designed for, it is formulated for sealed systems ..i.e.fuel injection. Heat from the engine will percolate fuel and leave the bowl empty if it is not running .
I could be wrong but even if the power valve leaks or is missing doesn't the fuel have to flow up to the discharge nozzle to leave the carb? this is above the fuel level so that would not drain the float bowl. I bet it is just what 97 said. Could be wrong.
I have the same problem on several cars, I have to many to keep all of them running . I put a cheep electric in line fuel pump with a spring loaded toggle switch so when I get in a car that I haven't driven for a while I just charge the line and carb and your good to go. Its also like carrying a spare fuel pump
As was stated, bench test for a leak. If no leak is found, I would suspect evaporation . This fuel of today evaporates very very quickly.
The 4150 has 1 power valve per 2 bowls, even if the PV has gone bad in the front bowl the rear bowl & accelerator pump should still work - no provision for PV back there (although some do have a 2nd PV). Let it sit for a few days, remove the air cleaner and cycle the throttle while looking down into it to see if either squirter is working, that will tell you what to do next and what needs to be fixed.
Bingo! Thats the reason quite few carbureted rods use a small electric pump to prime before start up.
Simple, and has been said... IT'S TODAY'S FUEL... Install an electric fuel pump, let it run a few seconds before turning the ignition key...all will be well..! The alcohol component in todays fuel evaporates much more quickly than pure gasoline, and that takes much of the gas with it. Mike
It's got to be the fuel itself, the "light ends"? I was convinced carb bowl was bone dry as after several days sitting the engine would need fairly long cranking to light off. Maybe 10 seconds or so. Just like the OP says. So instead of that, I'll pour a tablespoon of fuel down carb throat and it will then light off instantly no matter how long it has sat. Imagine my surprise though when removing the airhorn shows the fuel bowl with plenty of fuel, even after a month of sitting. Lots of complaints about this "feature" from Autolite/Holley users. What I should try maybe, is siphon some of the fuel that remains in the fuel bowl after sitting, and see if it has any zip left in it, by pouring that down the carb throat. I discovered that it will light off first time everytime with about 20 pumps or so, this shouldn't be necessary. It is weird.
20 pumps????? Damn! If the bowl is full, it should only take one pump shot to the floor to set the choke.....
Same symptom's , but guess I was stupid to think it was syphoning back to mechanical pump & tank. Put a fuel filter on it with a one way baffle and problem solved. Maybe I had diff. problem & maybe that was before the modern gas................................ So what your saying is you can fill a glass full of modern gas, sit it on the counter and 3 day's later it will be empty or close to it?
I know what it "should" do, and it operates perfectly otherwise except, after sitting for several days. It is really strange. This is also apparently a common problem, after searching different forum archives looking for remedies lots of folks observe the same..
I Also believe it evaporates much faster than years past. I also believe with the ethanol in the gas at engine shut off and hot heat rising from engine, the fuel rises in bowls till engine cools. This might cause some fuel to drain in the engine through the jets till the fuel cools. Then it is quite a bit lower in the bowl for two reasons.
If you truly believe the fuel is draining down into the engine, check to make sure that your oil level doesn't read over-full. Also take a whiff of the crankcase and see if you detect a distinctly gasoline smell.
A thread back from the dead. That makes it a "classic". You got'ta love 'em. Here's my 2 pence....... The fuel in my bowl was disappearing, too. On the advice of my betters, here, I bought the inline, temporary on, electric, booster pump (which I haven't spliced in yet) and I also got one of these squeeze 'primer bottles'. My fuel line must be good at keeping a full column of gas because it only takes a teaspoon dribbled in the carb to instantly start and run. I currently have E-10% in the gas can that I use for my mower so that's what's in the squeezer. This gives me the opportunity to observe the one or two ounces of fuel in the 'bottle' and I've noticed that it does thicken over time. Not good. Chapter 2 in my saga is...... I am fortunate to have 2 new gas stations in town in the last year that sell E-0, pure gas. (I think it's 90 octane, but don't quote me 'til I check.) The E-0 is what's in my '50 Chevy truck. It seems to have helped with the quicker-than-before starts, also. I plan to fill my lawnmower fuel can with the E-0 next time I top off the truck tank. Lawnmowers need a little love once in a while, too.
After installing 3/8” phenolic spacers under my WCFB dual quads will last at least 3 weeks. They are progressive and take a full single pump to start. I do have manifold crossover heat but it is restricted.