The Stovebolt Site Forums The Shop Area Engine Shop Leaking carb BIG gas LEAK

So I just got my truck back from the muffler shop and and have been fine tuning. So I have a 235 with fenton headers and intake (dual rochesters). The problem is gas is leaking out of the first carb (closest to the radiator and first in line from the fuel pump). Could it be to much pressure from the pump which is stock. If that is the case wouldn't it affect both carbs also I rebuilt the card and tried another spare carb with the same result.

little horse,

Not sure what the problem is, but I am darn near positive it isn't too much fuel pressure. The carburetors are on a common fuel line, so pressure seen by the front would be seen by the back too.

Is the carburetor leaking where the air horn screws to the body? This would be the uppermost gasket..a leak prone area on these carbs.

The float, when adjusted properly, should set
the fuel level below this gasket.

I would remove the carburetor that is leaking, check the float level, needle and seat for junk, any threaded connection for tightness, and all gaskets for tears or damage.

It is my understanding that the design of the air horn on the Rochester B (?) allows it to become warped during casting, and this warping is why it is hard to seal along its thin mating line.

Stuart

Stuart,
The leak is between base and the belly. Base being the part that bolts to the manifold and the belly being the part that is bottom half of the carb itself. It seemed odd that two carbs did it in the same place but even odder that the rear one didn't. Any other ideas. Thanks again to all

Check for cracks in the bowl casting. I've seen plenty of the Rochester model B with cracked bowls. If it's cracked you'll need to get a new one. Personally I'd suggest a Carter or Holley, they seem to hold up better in my opinion.

little horse,

I just looked at a exploded view of your carburetor, and there doesn't seem to be much going on in that gasket area between the float bowl (belly) and the base.

The accelerator pump rod goes through the casting near that area..I wonder if it could be leaking down and making it appear to be leaking in the base area.

I remember a little soft plug of some sort in the base of the float bowl (I think), but don't know if this could leak.

Regardless of what is leaking internally, the gasket on the bowl to base junction should NOT allow any fuel to reach the outside.

This might be a job for CARBKING....

Stuart

Little Horse,

My B Model also leaks there, but not enough that I bothered worrying aobut it (especially since it will be gone soon). I found that it leaks worse when it floods because of the floats sticking.

If it is a rebuilt carb, dso you think there is the possibility of a small perforation in the housing? That or the gasket did not seal properly. Not much to choose from really.

Good news the leak stoped. I took the carb off and took it apart to see what I could find. I found nothing to note but cleaned everything anyway before putting it back together (including gasket surfaces). I don't know what I did but it worked now if I can just get it to run smooth and continuous. I think my timing is a little off that and idle speed. It runs but won't run for a period of time longer than about 20 secs.
Thanks again for your help
Brian

try adjusting your idle speed first, then if that doesn't work try the timing.what's the truck sound like when it does run? Backfires? Sputtering? send some more info so we can help
-Lurch
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'61 Apache 10
If it ain't loud, I ain't interested

When it just starts it is fairly smooth, (tiny exhaust leak to be fixed later) doesn't backfire or pop. It just wants to die. I got it going and thought I had it and sure enough about 20-30 secs and it just slowed to a stop. I am running a 12v system with hei. Idle is what I am thinking but I am just not sure. I am focusing on the carbs. I am so close to taking it on it maiden voyage it is killing me. I bought it towed it home and took it apart. Never driven yet. SOOOO close.

Oh yeah I haven't been able to start it yet without a squirt of carb cleaner.

Mine does the same thing but usually the back carb after it sits awhile. It is the needle and seat sticking. Next time if it does it, tap on the front of the carb and see if it quits. I had the gross-jet needle and seats in it awhile and did not have that problem but went back to stock units the last rebuild. I thnk it just sits awhile and sticks. If it gets run more regularly, It does not happen.

Would that be the cause of it not wanting to start with gas not carb cleaner?

That could be, as carb cleaner is a bit thinner than gas. If it's been sitting any amount of time, the gas in the needle and seat will gum up just enough to make it stick. Most Gas starts to go bad in a couple of weeks if there is no new gas added to it. If that's not the case, try speeding up the idle, and clean out the carbs real well. You may also want to get some fuel stabilizer added to your gas.

-Lurch
------------
'61 Apache 10
If it ain't loud, I ain't interested

I have a 1954 Chevy 261 ci with a Model B Rochester carburetor. This carburetor has TWO holes in the throttle body where it mates to the insulating block to the manifold. One hole is perpendicular to the face and the other is at a slant. I also have a slightly older Model B carburetor and a slightly newer one. One of these other carburetors has one of the holes (at a slant) and the other has the other hole (perpendicular to the surface), but neither has both holes. (One of the holes might have been to operate a governor.)

I need to rebuild the two-hole carburetor. I got a kit from NAPA. It was the only one they said they listed. But then I read the ‘54 shop manual. The shop manual says that there are two different carburetors and, “The differences between carburetors are the sizes of the carburetor throat diameters and some of the jet orifices.”

So, before I open the kit and use it, will I be putting the wrong size jets/orifices, etc. (for a 235) into a carburetor designed for a 261? The NAPA people don’t know the answer. Also, how do I tell whether to allow one of the two holes to be blocked by the gasket and if so, which one?

This looks like a potential source of future mysterious symptoms that no one could then diagnose. On the other hand, it could be that none of the crucial different-sized parts are in the kit and the hole problem is not a real one and I shouldn’t worry.

Any help will be most appreciated. If there are indeed people who sell a kit for the 261 version I sure would like to get and use that. The rest of this engine deserves to have a nice carburetor.

the kit should work for either carb, the difference is more of a calibration thing, just slightly larger venturi for the larger engine. usually just gaskets & such in a kit, you clean & re-use your power piston & main jet. I use #000 steel wool to polish the power piston so it moved freely in the bore. With the carb disassembled, you can run a small wire through to determine which hole operates the power piston. that is the hole you need to line up with hole in bottom gasket. I think the other hole will be unused(blocked by the carb to throttle body gasket when assembled) brian

Thanks so much for the peace of mind!