Carburetor; what is letting gas seep out the venturies??

Thanks for looking,
I have an OEM 2bbl Carter on top of my 383, and I recently rebuilt it.. I think I made a mistake somehow, because the car will start and run fine until it's hot, then it balks and quits if I let it down to idle...

When it has stopped, I can smell gas, I pulled the air cleaner, and can see fuel dripping out around the lower throttle shaft onto the manifold, I can look into the venturi's and see gas dripping rapidly, like spilling, from the little brass pipe/nozzles in the center of both venturi's,

..so I think something that is supposed to stop gas from flowing freely (check valve anywhere?).. isn't working.. I mean, the engine is stopped and it's just emptying the float bowl.?!

If I wait 15 minutes, prop open the lower butterfly valves and let the visible cloud of gas vapor dissipate, and, I can get the car to fire up by stepping full throttle on the pedal.. then it'll last me another 10 minutes to limp home before it quits again..

Maybe there is also an extreme rich adjustment problem? ...but this is the OEM carb for the car.. I didn't think these OEM Carters had an external mixture setting.. other than the idle bypass air screw..

So I mostly suspect some kind of internal check valve problem

I'll rebuild it again, but I'm hoping you all might clue me in on what I might have done wrong so I don't repeat it... ?

Thanks,
- Art

Float is set too high ?

But otherwise welcome to the world of ethanol fuel , especially with the heat we have been having the last few days .

PS - The 2bbl rebuild was done 10 years ago, and I packed it up and sat it on a shelf waiting for the day I wanted it back on the 383..

.. so it wasn't a "fresh" build exactly..

More on that story here:
https://board.moparts.org/ubbthreads/ubbt...tml#Post2503075

Thanks John,
It was indeed an exceptionally hot day to be out and about... I thought briefly of vapor lock, and the engine does run a bit hot ... so are these symptoms consistent with vapor lock?

.. does the gas boil and the pressure spews it out anywhere?
- Art

Looks like you have bad needle and seat. The rubber in the assembly is probably dried out and disintigrating.
I had those exact symptoms on my Holley 500 cfm. Turned out to be the needle and seat.
I changed it and did a complete rebuild. Now, I don't even have to pump the gas when starting in the morning. Bump the key, hands free, starts right over. Also after a long run I let it sit 5 minutes, bump the starter fires right up. No pumping the gas. Let it sit 30 min, hour, two hours, 6 hours , etc; bump the key start without pumping the gas, starts right up.

Vapor lock is when the fuel turns to gas in the fuel lines and the pump can't pump it.

I suspect either the float set too high or the float has a hole in it, is it brass?

There could also be a chunk of "stuff" between the needle and the seat.
I got to pull the top off my grandson's 64 Chrysler Sunday afternoon because it was flooding over. I thought maybe the float was bad as well. We actually tested the float in a glass of water. We found what looks like it might have been part of a fuel hose stuck under the needle. Pulled it out, reassembled the carb, and drove it home.

My guess is that you have junk running through the needle and seat. Its time for a new inline gas filter, check the float, and maybe clean the junk out of the fuel bowl before it gets stuck in the small carb passages. I would also replace all the gas hoses on the car, don't forget the one back at the tank. Gene

The cause can be several things but the symptom is almost certainly too much fuel in the bowls. If the float level is set too high, or the needles and seats are not stopping incoming fuel, you will overfill the bowls causing your problem.

Thanks guys,
Much appreciated. Yeah, the fuel just flows down the barrels after shutdown... I have a rebuild kit ready to go, so I'll get it done after the weekend..
- Art

Hello Art, As said: bad needle/seat/float set wrong/linkage hanging up/debris kicked loose when the fuel rushes forward when you restart. lightly twirl the needle neoprene tapered tip between your thumb/forefinger to smooth it (as you know that is the shutoff valve). and a good filter before the carb.

Yep...good advice given here. On the Carter BBD the brass tube that sticks out and is cut at an angle is actually the bowl vent. No liquid fuel should ever come out of it. So by observing it when you did, that was most of the diagnosis.

If it's been run this way for very long you'll also find the spark plugs to be fouled (black and possibly wet depending on how recent). Also check the oil to make sure it hasn't been contaminated by large amounts of fuel.

Yes the gas does boil and can spit out, it's really bad with carter afb type carbs. Your symptom sound similar to someone else I know that had a similar problem, once the engine got hot it was stall pulling up to a stop and be hard to restart ...

But as said first thing to do is check needle and seat and check the float level.

A quick update - got the car running fine again..

Pulled the carb, opened the top, didn't see anything obvious. I adjusted the floats a little lower, reset the idle mixture screws to 2 turns out, and cleaned the needles.. put it back on and it runs fine, took it around the block 5-6 times, checked it, then went for a 4 miles drive.. no free-flowing fuel pouring out anymore.

..and it's also not a 95F day out today...

..so I ordered a rebuild kit from Larry Isgro Carburetors on Long Island, NY just in case - been dealing w him for over 15 years now. His first suggestions were the same as yours - adjust floats and check for any debris stuck at the needles.

Thanks again guys,
- Art