Carter BB1 Updraft Carburetor

[djr71]

Hi

I have a 1932 Plymouth PB Roadster, fuel is pouring out of the bottom of the carb. I noticed something has fallen out of it.

I looked at a diagram and it says it's a pressure valve which I didn't think it would be at the bottom. I talked with Mike's Carburetors and they said it's just a cleaning port and all I need to do is put a bolt in there. They do not sell the bolt or know the size.

Any idea what it is? Any help would be greatly appreciated.

Thanks

Doug

[Mark Shaw]

[keiser31]

Maybe these will help....

[djr71]

Thank you guys.

[carbking]

The picture is too close to the port to be certain.

 

If that is a port on the very bottom of the air intake portion of the lower casting:

 

EDIT: the port I am guessing is pictured on form 4360M posted by keiser31. If you look at the carburetor pictured to the left, this port is directly above the "1" in "1 inch flange size" in the caption.

 

It is not either a pressure port or a cleaning port; it is a drain/vent.

 

Most were left open to the atmosphere, as is yours.

 

A few have a sintered brass pressed in plug (that can breathe or drain), it is NOT a seal.

 

The marine versions have a drip tube fitting threaded into the port. The fitting is connected to a drip tube (generally just a loop in a length of copper tubing) and the other end connected to a vacuum source (most BB-1 updrafts have a vacuum plug at the top of the throttle body).

 

Putting a bolt in the hole will NOT stop the leak, the fuel will simply leak out the front of the intake. This was the reason for the drain/vent to be machined in the casting. 

 

The leak could be a number of issues:

 

(1) electric fuel pump producing more than about 2 psi OR pressure pump of any pressure and the gravity flow fuel valve.

(2) defective float

(3) defective float setting

(4) defective fuel valve

(5) RARE - cracked casting

(6) If the leak only occurs when cranking, defective intake valve

(7) If the leak occurs only after the engine was running, then turned off, then the leak stopped after a few minutes - it is the fuel above the throttle plate and in the intake that drops down when the vacuum leaves.

 

If you want to believe that plugging the hole will stop the leak, it is 1/8 pipe thread. Your FLAPS will carry an 1/8 inch pipe plug.

 

If I did not guess the correct location from your picture, ignore the above.

 

Jon

Edited June 21, 2023 by carbking (see edit history)

[djr71]

Thank you Carbking

[djr71]

here is a better picture 

 

thanks