Holley 1920 Carb question 225 - 6

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louisproper

louisproper

Cuda64
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The Holley 1920 carb on my 64 Barracuda is dumping gasoline out onto the intake manifold. After pulling and cleaning the exterior, there is a small hole or chip on the bottom 'cast tube' running along the bowl on the back side.

It looks like it is actually a drilled hole, but I am just waiting for the dumped gas to ignite.

Is this hole supposed to be there? is this the curb idle vent I read about?

I sent Holley Tech the question on Sunday and they have chosen not to answer yet.

This is holding up putting the car back on the road and is killing me.

Lou
 
The most likely thing to cause gas to overflow is that the carb float is not maintaining the bowl level. Possibilities - the float sunk (has a hole, filled with gas), debris is holding the needle open, the needle valve is old and the rubber bad, something in the pivot is sticking.
 
Can't clearly see the hole you're pointing at. It's not the calibration hole present on many pre-1970 carburetors of all make and barrel count; that'd be over on the other side of the carb if yours has it. Could be the accelerator pump chamber vent. It doesn't sound as if you've verified that this is where the fuel is actually leaking from. The leak point could be from the external bowl vent in the case of a stuck or sunk float or a faulty inlet needle/seat. It could be from the bowl cover gasket. It could be from that hole you're pointing at if there are internal faults in the carb. It could even be from a cracked carb casting.

The "curb idle vent" (external bowl vent) is atop the carburetor, right up front, capped by a little round rubber hat on the end of a pivot lever. When the throttle is closed (curb idle) the hat is lifted off its seat, thus venting the carb bowl.

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

The float in a 1920 cannot "fill" with gasoline or get a hole in it; it's a nitrophyll foam float, not a hollow brass one. But they can take on fuel and grow heavy, causing the same problems. Also the float counterspring must be present.

Have you been through the carb with a rebuild kit and a new float yet?
 
Dan

Thank you for getting me to the tech articles. Did wonders for knowing what I am looking for.

I reset the float height - not really that far off, and put it all back together and tightened up.

back on the car, ran fine, but the same gasoline dump when the accelerator was pushed.

looking at the tech diagrams you sent me access to, the culprit vent is the accelerator pump air chamber vent. The diagrams show this as an air to air vent for the air chamber behind the accelerator pump diaphragm.

I believe the issue is a torn or holed accelerator diaphragm. I am going to pull the carb off again and see if I can put my hands on a rebuild kit. I hope the accelerator pump diaphragm is part of the kit.

BTW, inside has been very clean and no visible trash. car had a fuel line filter on it when I bought it and that was one of the first things I replaced.

Lou
 
louisproper said:
I believe the issue is a torn or holed accelerator diaphragm. I am going to pull the carb off again and see if I can put my hands on a rebuild kit. I hope the accelerator pump diaphragm is part of the kit.
Click to expand...

Er...y'mean you opened and closed the carburetor without a rebuild kit? Yikes! That's a terrific way to set the car on fire. That bowl gasket is a one-use-only item. Yes, you need a rebuild kit, and you should put in a new float, too. Walker kit number 15480A, Walker float 100-14.
 
I got the carb rebuild kit through local NAPA, only have NAPA and Advance Auto here, Advance had a corresponding number but could not source the supplier or prove what carb the kit was for.

Anyway, new kit in, could not order float thru local stores, but was able to weigh it at NAPA, carb kit solved the problem, was a lot easier to do than envisioned (for you other all thumbs guys out there). The accelerator pump diaphragm indeed was worn thru and allowing gasoline to pour into the air only chamber.

took car out this morning for a road test after several static runs to make sure all tightened up and no leaks. (first road test since front brake complete rebuild)

(BTW--on earlier exercise, before new carb kit, the bowl gasket did not leak at all with 5 opening and closing and 2 minute runs looking for leaks).

Dan, thanks for the help, and tech data links.

new avatar posted since I got car out of garage.

Lou
 
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