weber fuel problem

[sono veL.O.ce]

My dcoe 40s are giving me a strange problem.
when I have the car running, mostly at idle (the car runs but I'm not driving it yet) but also blipping the throttle. I have fuel coming back the wrong way through the primary venturis. and dripping on the fender wall. YIKES! FIRE HAZARD!

The carbs are freshly rebuilt, including new float needle and springs.

I use a low pressure(4-6psi), electric, carter fuel pump which is specified for weber doces.This was previously a SPICA injected car.
I don't belive the pump is the problem as I can leave the key in the "on" position (fuel pump running, car not running) and pump the gas pedal without any fuel leakage, I can also remove the inspection cover and it doesn't seem like the fuel level is out of control.

Tomorrow I am going to recheck the float level. I set them VERY carefully at 8 and 15mm, but am re-checking them first thing just the same.

"reversion" doesn't seem likely to me as I experience the phenomon even during Idle.

At this point it seems like the mixture is coming from the primary venturi, dripping out at idle and blowing out when I blip the throttle.

I'm stumped. everything about it seems to point to too much fuel in the float bowl, except that it only happens when the car is running and not when only the fuel pump is running. Im calling in my friend who is real good with webers to help me in the afternoon, but thought I'd also post here to see if anyone has any leads.

[tubut]

A couple of suggestions:

1. Make sure thst the carbs are sloping downwards (towards the intake manifold) at an angle of 5 degrees, as specified by Weber. (I assume you have a proper carb support on the air intake side).

2. If necessary, change the air horns from straight ones to the ones that bend upward.

[sono veL.O.ce]

at this point its just the carbs, with no support plate and no air horns. mounted using factory softmounts (the kind with the bridge between carbs). Onto a European 1600 manifold that I bored out and matched to the carbs and head.

I am going to use stacks and an air filter on a support plate but I'm trying to fit the biggest filter I can so I'm custom making the support plate and not finished.

May I ask how you figure the angle plays into it?

Thanks for the input.

[John M]

Hey Sono:

How is the synchronization? Is it just one carb or both? And how much gas coming out? Is it more like a backfire through the carbs? Check the throttle plates in the carbs and make sure they are synchronized. How about the mixture? What are they set at? I would also consider the intake cam timing being off.

Best Regards,
John M

[sono veL.O.ce]

both carbs, throttle plates synch'd, I'd say there's at least as much coming out as there is going in. enough so that after i start it, and walk around the hood to have a look, there is a bunch of drips going down the fender. when i blip, its like a very wet sneeze.

hows that for a unit of measurement

Jetting is off at the moment:
running 34 venturis (these stay in)
with a 145 main (might drop this down to a 135/140)
180 air corrector (problably moving up with this, i'll start with a 210)
f16 emulsion tubes
accel pump jet is a 35
idle jet is a 50f9

[John M]

That is a bunch but doesn't sound like you are overflowing the bowl. It literally pours out if you overflow the bowl.

I don't think its your jetting. 145 is probably too much on a stock motor but I don't think it would do what you are describing. 180 on the air corrector is on the rich side but I don't think those kick in until you are making some significant rpms. I really doubt that this has anything to do with the problem, but how many 360 degree turns are you out on the mixture screws? Also...how many turns are you into the idle adjustment on the 3/4 carb? Make sure you are not compensating with the carb idle for an incorrect timing at the distributor.

Just to bounce a few far fetched things off the wall.......Like you said, if gas not coming out when not running but key on....that rules out a stuck float. I think I would pull the jets all out just for piece of mind if you haven't already. Make sure they are all pressed together correctly and then reseat them all. With both carbs doing it...it really makes me think that the intake cam timing might be off. Have you adjusted the cams recently? Maybe added performance cams? Some of the performance cams don't time off the original marks on the journal caps. The journal cap must be degree'd to create a new mark corresponding to the new camshaft. Just a wild thought or two.

Best Regards,
John M

[sono veL.O.ce]

I fixed this a long time ago but forgot to post the solution.

Upon close inspection using a flashlight and mirror I could see the fuel was dripping from the acellerator jet , this is the lowest spot in the venturi so it wasn't entirely conclusive but I figured I should check the jets & circuit.
the jets were clean and smooth, so i pulled the carbs form the car and took them to the bench.
there is a checkvalve at the bottom of the float bowl that starts the circuit. Ipulled the valve and blew through it to be sure it was functioning, then I pulled the pistons and checked their condition, they looked good. blew some air throught the circuit and reassembled. put them back on the car, fired it up AND....
FIXED!!!

My best guess (based on the fact that it was happening in all four venturis on both carbs, that the leak was continuous, and that my take-apart and reassembly fixed it) is that the check valves at the bottom of the float bowl were just stuck open a bit and needed to be blown on to loosen them up. this makes the most sense to me cuz then only two mechanical pieces being stuck caused the four leaky venturies as opposed to four sets of jets/pistons/passages...that would be a little too much of a coincidence.

Hope no one lost sleep over this one (I doubt anyone did), and that this thread can help somone out in the future(check those check-valves!).
buona notte,
L.O.