Fuel System: Carb

[mapman]

Working on my’51Commander carb and I found 2 small holes in the base above the butterfly’s. It is tucked up under the float bowl but is open to unfiltered air. I don’t find them in the illustrations in the shop manual. They appear to be factory but I see no reason for them to be there. Does anyone know what they are for?

[Mike Van Veghten]

Many factory carburetors have similar holes.
Exactly why they are there, no I do not know for sure. But they are of no harm. They are not vacuum leaks if that's your concern. The are above the throttle blades, so in fact, they are just letting a little more air into the airstream in the venturis.

I have a coupla thoughts what they may be doing, but...

Mike

[doofus]

I always thought they were their to vent fuel to the outside air to prevent flooding,when an engine is shut down the fuel caught above the butterflies has to go somewhere right? to the outside seemed better than down the carb throat. Luck Doofus

[mapman]

What ever they were there for I made some brass plugs and filled them. I was having problems with a flat spot in the acceleration and was looking for leaks. I will see what happens next. I suspected a bad acceleration circuit and found this as I was cleaning. Maybe they are there to help prevent flooding when the choke is closed? More later when I can try it out.

[Dwain G.]

The factory (and/or Stromberg) drilled those holes to combat hard start hot. I knew a old mechanic that had been doing that for years on other cars, he claimed to prevent icing.

Click to expand

[mapman]

Thank you Dwain G. If I experience hot start problems I will knock the plugs out again. For now the car has greatly improved drivability with almost no hesitation when accelerating.
Rob