Need some carb help! Autolite 1100 rebuilt but it’s dripping fuel down the Venturi off idle!

[cobra5laddict]

Happy holidays all!

I spent some time off from work rebuilding my autolite 1100 for my 66 mustang with load O matic. I’m aware of the upgrade benefit to dual advance distributor but at this point I’m sticking with the original set up.

Using a kit from Mike’s carbs, I completed a full rebuild and all went well. It idles great but once I get above the idle circuit (1800 ish rpm held steady) the car stumbles pretty bad (this is not under load, just my garage). I put on a full face mask and watched down the carb throat while runnings and off idle, fuel drips down the Venturi holding the throttle (simulating an at cruise situation). The accelerator pump gives a good atomized spray when you blip the throttle, it revs up quick and smooth. It’s the darn sustained throttle above idle that is dripping and stumbling the engine.

I have a carb with dashpot (auto trans) so I have 4 check balls all in the correct locations as well as the check weight. Any ideas here?

 

[Econoline]

Maybe a check ball isn't seating well? Do you (gently)drift them into their seats?

 

[bubba22349]

Next Recheck the fuel float level setting and then also check the fuel pumps pressure. Good luck

 

[drag-200stang]

Carburetor icing can cause that...Is it cooler and damp out?

 

[cobra5laddict]

I don’t believe anything is icing up, this is just running in my garage not road tested at this point.

Float level in the rebuild manual said 1-3/32. It was pretty spot on when I adjusted it on the bench. It did take quite a bit of adjustment from where the float was set before. Does that measurement seem off to anyone else?

I didn’t tap the balls to seat them so I will pull the top off, seat the balls gently and check the float level again. Any other ideas?

 

[chad]

"...Carburetor icing..."
nuttin ta do w/"bein out of the garage" or in.
A venturi causes speeding up - in a carb this can cause the H2O in the petrol to freeze out inta
ice crystals. Hot humid days we got it in the ol days, puta an ol wooden clothes pin on rubber fuel line to correct back then (slo down fuel I guess...

 

[cobra5laddict]

Interesting explanation on carb icing.

Fuel literally dribbling down the throat of the carb when holding the throttle at approx 1800-2000 and probably above just seems wrong to me and naturally make sense that it is attributable to the stumble. Is that normal operation? I would assume the fuel would be atomized better (when I goose the throttle, the fuel shot is a nice spray.)

 

[chad]

even beddah (actually 4 ur problem) "LOM/SCV"...

 

[Econoline]

Float level can cause odd problems ime. With this carb float level is float perpendicular to the top, upside down. That's your baseline float setting. If anything add a little, lean wise with your problem. But seat those balls first. When they're out examine the seats with a flashlight or under lighted magnification. It doesn't take much fuel pressure to run/hold rpm off load. Fueling doesn't feel like the problem to me. Start with the simple stuff. Filters, float level ect. There's not much to go wrong with mechanical fuel pumps if the diaphragm is intact. It's usually the needle or float that's causing a problem in that regard. Sometimes I feel like we get too many knee jerk 'check the fuel pump/output' replies and it's a messy pita to do. If the filter is good and your confident the tank/sock is clean and the pump isn't leaking into the crankcase, it's probably not the fuel pump. Esp if you're getting too much fuel as you are.

 

[cobra5laddict]

To set the float slightly more lean, I would increase the dimension on the float setting correct? Reducing the fuel level in the bowl correct?

 

[bubba22349]

Yes set the float so it's setting up a little higher than level this will lower the fuel level a little.

 

[Econoline]

To set the float slightly more lean, I would increase the dimension on the float setting correct? Reducing the fuel level in the bowl correct?

Yes. The float lower in the bowl when the needle seats. It's like setting your toilet tank float to get more flush but in reverse.