'53 Super Stromberg Carb Vent

[SJF1948]

I have a Stromberg 2bbl on my 322, I'm running an electric fuel pump with 4-5 psi output. The carb will spit out raw gas every 5 minutes or so from the bowl vent on the air horn. The engine seems to stumble for a second then recover. The shop manual says this is to "vent the float chamber to allow fuel to be smoothly withdrawn through various systems" 

The amount of fuel spit out is very small, evaporates quickly, but not what I would consider a safe situation!

I have cleaned and rebuilt the carb prior to putting my car on the road, float level is set to specs. Any thoughts?

 

[carbking]

Fuel setting is 21/32 below top of lower casting at 5 psi.

 

The electric pump is right on the edge of too much pressure. Have you actually tested the pressure with a pressure gauge?

 

Jon.

[60FlatTop]

That fuel filter looks similar to a 1930s AC fuel pump surge chamber but mounted at 90 degrees. It may be performing an unintended function. Can't say specifically but it looks suspicious to me, If I was having a problem I would eliminate it.

 

The best way to cure untenable problems is to remove the improvements.

 

I am not a big improvement or filter guy anyway.

 

I read a lot about carburetor problems on this forum. I lot are related to leakage at vent holes. Besides allowing atmospheric pressure to the float bowl the vents also provide a pressure differential to distribution tubes in various passages for fuel delivery. If fuel is spilling out those flows can't be right either and could exacerbate (in the true meaning) something that ain't right to begin with. I remember my best carburetor advice: "There are too many variables in carburetion to define as a science. It must be treated as an art."   Tom Toal, The Rochester Carburetor Man.

[EmTee]

1 hour ago, 60FlatTop said:

"There are too many variables in carburetion to define as a science. It must be treated as an art."   Tom Toal, The Rochester Carburetor Man.

You just need to derive the missing equations... 

[SJF1948]

I have not run a pressure check on the line at the carb, but I will as soon as I put the transmission back in.... another story for another topic! I did find a video on YouTube showing a pressure reading of 4.5 psi, deadheaded at the carb running the same pump I have installed. If my pump does in fact exceed 4.5-5 psi my options are a fuel pressure regulator or locate a pump with less discharge pressure. Throttling a centrifugal pump outside it's curve has its problems as well.

 

I'll admit, I'm not up to speed on Strombergs, but I'm getting there. Back in the day it was Rochester, Carter, Holley, Autolite, MotorCraft, etc. Your comment on the fuel level reminded me about the plug in the side of the float chamber which I assume can be removed to check the fuel level while running??? This I can check initially with running the pump only, then follow up at idle. 

 

I will add that my rebuild kit from CARS, Inc. is a Daytona Parts Co. kit. This uses a flat disc float valve instead of the usual tapered float valve. Other than spitting raw fuel out occasionally, the carb seems to be doing the job.

 

As for the 1930s AC fuel pump surge chamber, I have no idea what that is, but what the photo shows is a 2022 Mr. Gasket in-line fuel filter. This replaced the O.E. sediment bowl filter only because I was having trouble finding a gasket and filter stone for it. Also not a fan of the Mr. Gasket filter.

[SJF1948]

Follow-up on the fuel spitting Stromberg. I replaced the Mr. Gasket in-line filter with the original Carter sediment bowl filter and installed a pressure gauge upstream of the filter. At idle, pressure is 4.5 psi. I removed the float bowl plug and at idle the fuel level is right at the bottom of the hole. No other modifications, and no more fuel spitting! After several local drives at varying speeds there seems to be no problems with the carb. 

I did contact Carter about any potential problems with installing a dead-head pressure regulator on their pump if necessary. According to them there is no problem throttling their pump a few psi. I have not installed a regulator and at this point don't intend to.

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