58 Rochester fuel slosh issue?

[Smartin]

I've been plagued by this issue with two cars now, and have not figured it out.  It only seems to be an issue when I am turning left...for the most part.  The car will nose over like it's either running out of fuel, or fuel is dumping into the carb and choking the engine.

 

Has anyone experienced this?

[NTX5467]

Check for air horn warpage.  This would result in the lh float bowl not sealing and letting fuel from the bowl transfer into the venturi area.

 

Some 2bbls, notable Stromberg WWC morels on Chryslers, plus the later Holley 2210 2bbls, are prone to this situation.  Only thing is that on the Strombergs, where the non-sealing happens is at the rear of the float bowl, where the vacuum passage that works the power valve piston.  10mpg all of the time, plus in colder weather, at certain choke angles, it'll pull fuel out of the bowl into the venturis.  Holley came out with a kit to fix, but all I could do with the Strombergs was to make a sandwich air horn gasket.

 

What causes it?  The two-piece air cleaner assemblies AND the desire to have them "down tight".  Over time, too much wing nut torque will pull the air cleaner stud and surrounding casting upward, which results in the air horn not sealing against the throttle body as it should.  How many times have we put an extra 1/2 turn on that wing nut to ensure the air filter was sealing against the innards of that filter case?  For good measure?

 

This is my gut suspicion.  I suspect that if you remove the air horn from the throttle body, you might discover evidence of fuel moving from the particular float bowl into the venturi area.  Or with a new air horn gasket, a lighter imprint area on the new gasket, in that area.

 

The old-line Chrysler service manager that told me about this in the later 1960s said that he'd taken a piece of glass and a long flat file to "level" the casting for good gasket sealing.  Past that, not tightening down the air cleaner wing nut was important.  Perhaps to ensure air filter element sealing within the housing, a thin layer of rubber gasket material could be placed underneath the filter element so that the two halves of the housing didn't quite contact each other so that we'd know everything was sealing within the housing?

 

Please advise what you find.

 

NTX5467

[Beemon]

I guess this is a common problem. Carb King told me there was a factory fix that involved installing a bushing in the choke arm hole I think.

[NTX5467]

One thing I just thought about is whether it's a "carb" issue or a fuel tank baffle issue?  Or is this issue fuel tank level sensitive?

 

NTX5467

[carbking]

The issue exists with some Rochester 4-GC (4-Jet) and Carter WCFB carburetors. THERE ARE FACTORY SERVICE BULLETINS ON BOTH!

 

There is a vacuum passage that runs vertically from the throttle body through the bowl to the airhorn to activate the automatic choke. If/when the airhorn gasket deteriorates in the area of the passage between the bowl and airhorn, fuel slosh will be pulled into the vacuum passage on hard left turns, causing a temporary rich hesitation or stall.

 

Both Rochester and Carter offered service "kits" (a set of instructions, a bushing, and a gasket). THIS IS A MACHINE SHOP OPERATION! The passage in the bowl is milled slightly oversize to a depth of (forgot exactly) maybe 1/8 inch and the bushing is pressed into the passage. The passage in the airhorn is likewise milled but slightly larger oversize so the bushing pressed into the bowl will slip into the oversize area in the airhorn. The redesigned airhorn gasket has a slightly larger hole to accomodate the bushing.

 

The bushing prevents the fuel slosh from entering into the vacuum passage.

 

Jon

Edited March 14, 2017 by carbking (see edit history)

[NTX5467]

Interesting!

 

NTX5467

[JohnO]

I had this problem on my 61 Invicta with a Rochester 4GC. Without fail, it would always bog when turning right and going uphill. At other times it was somewhat intermittent.  I bought a Carter AFB off the internet and rebuilt it. Problem solved. It had to be something in the carburetor.