My car ran fine all summer with no issues. Went to start it recently after it had sat for a month or so. It wouldn't start and seemed like maybe it was flooded. Pulled the plugs out and sure enough they were drenched in gas. Cleaned them up and reinstalled. Car started right up. Parked it and about a week later, the same thing happened and again I pulled and cleaned the plugs. Started right up. Repeat once more today. What is likely wrong with the carb to cause of the flooding while the car is just sitting in the garage? Carb is an Edelbrock 750.

I would guess excess fuel pressure pushing thru the needle and seat. this could happen thru heat after the carb sits a few minutes after running, too much fuel pressure, wrong float level or some dirt in the needle and seats. I have had needle and seats gum up and stick open or closed. take the carb apart and look for something and do a hot fuel pressure check.

Needle & seat gummed up & sticking, time for a carb rebuild

Float stuck open.

How do any of the above flood an engine that isn't running?

Kevin

An unvented fuel tank can push gas past the needle/seat when the temperature goes up. Plugged bleeds can lead to a siphon effect in the carburetor but would affect how it runs. Is it rich? The AFB/AVS carbs aren't supposed to do this (leak below float level).

Don't run it until you figure it out. The oil is most likely contaminated with gas.

The guy lives in Detroit, it hasn't been hot enough in 3 months to cause gas in the tank to swell that much !!

Even if the engine flooded from heat soak, it appears to have sat long enough between startups for the gas to have evaporated off the plugs.

So my conclusion is its flooding at startup. Lift the hood, remove the air cleaner and look down the carb while someone's cranks it over. Make sure they are NOT stepping on the gas pedal. If gas is pouring in, check for something sticking the float(s) open. It takes a LOT of pressure to over power floats believe it or not. If you concerned about a backfire blowing your head off, remove the coil wire so the engine doesn't get a spark.

The liquid won't expand much either way, it's the air/vapor in the tank that tries to expand, pushing out whatever is in the way.

Another possibility is the main-well plugs at the bottom of the carb are porous. The plugs are aluminum and may become loose or corrode. Remove the carb. fill with fuel, elevate and watch for seepage out the bottom. Common problem on the older Q-jets. Not so much on the Edelbrock/Carter type.

Whatever, you missed the point ... it hasn't been that hot !!

Easy,,re-do your test with the gas cap off.

THIS; Had an issue w/a billet 850ish carb I built for Shane Studly and his stocker Mopar wagon. Ran great till he topped off the tank then the pressure in the tank literally crushed the ft. brass float(which I no longer use in builds) sticking the needle n seat flooding the car to the point of filling the crankcase w/gallons of gas. Solution, He added a vent to the filler neck and problem solved.....Especially important w/an elec. fuel pump....

Still dealing with this issue. Is it possible for a fuel pump to pump too much fuel when it goes bad? I took the Eddy carb off today and put another one on that I have that came off of a running car a little while back. When I started cranking the motor, once gas got up to the carb it started pouring out all over the place from the top of the carb and also the plugs flooded again.

Sounds like you have gunk in the gas tank sticking the floats opened
I would take the tops off of both carbs and remove the needles to see if the Viton tips have stuff stuck on them or stuck up in the seats in them
Stuff happens hat we don't like but we still have to deal with those problem to correct them, correct

Yes if a mechanical fuel pump air diaphragm hardens you can see an increase in pressure. Doing some of the test recommended would help you isolate. Pressure test, inspect the needle and seat. Something changed from the layover. Since you changed carb it may be fuel system pressure. But a sitting carb even if running previously can have the same issues. So unless you move a carb from a running car directly, you might not be able to cross it off the list.

By the way, even with a non vented gas cap, aren't gas tanks vented twice anyway? Once from rear and one from front via the overflows?

I was just watching some videos on You Tube about checking and adjusting Edelbrock floats. I am going to pull the top off the carb to make sure the floats are not stuck and at the correct position and also that the needles/seats are clean. Is it necessary to replace the gasket between the top and the body of the carb when putting the top back on or can I reuse the existing gasket if it's not broken or brittle?

Does it do it if the car isn't heat soaked? Sometimes the fuel will percolate after you shut it down as it has more time to absorb the heat, it can actually start to dribble out of the boosters, especially if the float is set on the high side.

Yes, it does it when the engine is cold.