4gc flooding

[Guest smokeytires]

Hello I'm new to this forum and need some help on a 4gc carburator. I have put a kit in the carb its in a 56 caddy eldorador. It starts and runs for approximately 30 seconds and floods out the top of the carb. I have set and reset at different heights to try to pinpoint the problem. Still floods out. Any suggestions would be appreciated. Thank you.

[Larry Schramm]

Have you checked your float? Sounds like it is not buoyant to close off the fuel. Just a thought.

[Guest smokeytires]

Have you checked your float? Sounds like it is not buoyant to close off the fuel. Just a thought.

Couldn't feel any fuel inside of the float. My be minimal amount. Any advice on testing it.

[Larry Schramm]

Is the float brass or composite/cork? I am guessing brass. If you do not hear anything inside of a brass float would guess good. If the float is not brass then would look to replace it. If the float is good, would look carefully at the seat where the float needle goes in the body for a damaged needle, cracks, or debris causing fuel to leak past the needle & seat.

On another kind of doubtful, what is the fuel pressure? Did someone put in an electric fuel pump that might have a higher pressure than specification for the operating fuel pressure for this vehicle.

Just a couple of thoughts.

[JohnD1956]

I don't think a shake test is conclusive. Examine the seams. All that is needed is one pinhole on any of the four. I had this last year and we found thin solder on one seam.

[Guest smokeytires]

Its a brass float. Needle and seat is new but I'll check it out. Fuel pump is a stock new one. It had a loading up problem before the rebuilt but never flooded out. I'll check out the needle and seat and the float and see what I find. Thank you.

[carbking]

Brass floats may be tested by submerging in hot water. The hot water will cause the air inside the float to expand. Any pinhole will immediately show by a stream of bubbles.

Adjustments of floats for the 4G series are best made with a special factory float gauge; as both lateral as well as vertical adjustment is necessary.

Another possibility: Rochester often used DIFFERENT floats for the primary and secondary; however, if one doesn't know what to look for, they ALL LOOK THE SAME! The difference is in the placement of the arm on the pontoons. As maximum buoyancy is obtained when the arm is perpendicular (right angle) to the valve, the pontoons are soldered on to the arm at different heights, if a different height adjustment is necessary for primary and secondary. 19 different floats were used in the 4G series carburetors. They may physically interchange, and not function properly.

Since it was loading up before you rebuilt it, just possible some previous owner, when needing a float said "Well, *&^%$, they're all the same, and I have this parts carb. I'll use a float from it.".

Jon.

Edited September 16, 2013 by carbking (see edit history)

[Guest smokeytires]

I agree with what your saying on the previous builder swapping things. The base gasket was a problem as it didn't match any gaskets I could find. I found one that was close but not quite I had to epoxy the edge to make it work. My neighbor ( the owner )is kind of on the cheap side. I'm just trying to get it running for him. It was previously rebuilt with the wronge base gasket. The carb number goes to a 1956 caddy. Base I don't know. I'll check the float like you recommended and see what happens. Do you have any ideas on setting the idle bypass on these I've never see this before. Thank you.

[carbking]

The idle bypass is the method used on this carburetor for setting the idle RPM. Think of it as a metered vacuum leak. The more vacuum leaked, the higher the RPM. As an initial setting, try 1 full turn from lightly seated on the two idle mixture control screws, and 1 1/2 turns on the idle bypass screw. If the idle RPM is too high, turn the bypass in; too low turn it out.

Epoxy around fuel is a BAAAADDDDD idea! By base gasket, are you referring to the throttle body gasket (between the throttle body and bowl) or the flange mounting gasket (between the throttle body and the intake manifold)? If you are referring to the flange mounting gasket, some of those manifolds have exhaust coming up to the base of the carb to help atomize the mixture. The incorrect gasket will cause exhaust pressure where there should not be pressure, and create a flooding condition.

Kits containing the correct gaskets ARE available. As for "being on the cheap side" (your words describing the owner); show him one of the old Fram commercials "pay me now, or pay me later". Carburetor kits are very inexpensive compared to engine fires.

Jon.