The Stovebolt Site Forums The Shop Area Engine Shop Carburetor leak

Can someone help me identify the specific model Rochester carburetor I have and if you think a rebuild kit will fix the leak. 1954 3100 with the original 235 and carburetor. I attached a video of the leak



UPDATE
SO, SINCE POSTING THIS I HAVE BEEN HAVING SECOND THOUGHTS ABOUT REBUILDING THE CARBURETOR. I AM THINK ABOUT JUST BUYING A REPLACEMENT. FROM A QUICK SEARCH IT LOOKS LIKE A REBUILT REPLACEMENT IS ABOUT $200. ANY RECOMENDATIONS? ROCHESTER VS. CARTER OR SOMETHING ELSE?

RUN- - - -do not walk away from a "rebuilt" carburetor. They're assembled from a bunch of mismatched bits and pieces and the odds of getting a good one are approximately equal to finding a chicken with lips. You have a very simple flooding problem, caused by either a bad needle valve, a float full of gasoline, dirt in the fuel, or "all of the above". Unless there's a sheet metal identification tag under one of the screws attaching the air horn to the body of the carb, it's impossible to get an accurate ID of a Rochester B. A generic rebuilding kit, a new float, and a good cleanup of all the hard parts in a solution of dishwashing detergent and boiling water should clean up the carb you have to be as good as, or better than some unknown "rebuilt" carb. The boiling detergent softens the deposits in the passageways, and a rinse with boiling water followed by massive amounts of compressed air through all the passageways to blow all the crud out will put the majority of carburetors back into good condition. Look up Jon G's method of straightening a warped air horn that makes a lot of the Rochester carbs run too rich due to vacuum leaks.

"The ABC's of carburetion- - - -"Always Buy Carter"!
Jerry

i have this same carb on my '58 235 with an oil bath air cleaner. On an hour long trip to a show, I noticed that I have oil coming out of the butterfly rod just under shoulder where the oil bath air cleaner is mounted. I have not changed the oil or cleaned the air cleaner media in a year plus time. Any idea what would make the air cleaner oil come out of the rod hole ? The air cleaner bowl is filled to the correct marked level, I haven't added any oil to the air cleaner.....

Are you certain it is oil? Or could it be gasoline? Rochester B carburetors are notorious for leaking...all over the place. Please let us know.
Best regards,

Like I have said before "The best way to fix a Rochester B is to replace it with a Carter YF."

I tired rebuilding my old Rochester myself but it leaked just like it was before I started. It must have warped. I bought a rebuilt carb from BFIC www.carbsonly.com. They do nothing but carbs and rebuild them in their shop. they do not send them out. They also have a large number in stock. I contacted them on a Monday and had the crab shipped from California to Kentucky. I received in on Friday the same week. 15 minutes later it was bolt on a my 54 was running like a champ. A simple idol adjustment and I was good to go.

I had a similar problem a few years back when I had my Rochester. Check your float setting.

It seems like a long way for gas to go to get out of the butterfly shaft hole from the bowl. It starts & runs good, no hesitation. I will give the shop (Carolina Carburetors https://www.mycarburetordoctor.com/about-us ) that did rebuild on it to find out what they say about it tomorrow.

The Rochester B, BC, BV usually (maybe 90%) have a warping problem.
It's caused by material decomposition (sometimes called zinc creep), age and design.
Attempts to correct the warp has had some short term successes (lasts maybe 5 years).
The direct replacement is the Carter YF 2100S, if you can find one, is the preferred choice (use an Ethanol resistant rebuild kit).
There are other replacement carburetor options but the discussions can become quite long.

If you use your truck as a farm truck, as long as it will start and run, it doesn't matter.
If you use your truck infrequently (drive on Sundays, car show or parade), it may be okay.
If you use your truck as a driver, find a better carburetor and place the Rochester on the shelf.

Please check your PM. I have sent you a message about a Carter.

A warped Rochester won't leak gas all over the place. The warped area is above the top of the bowl.
The warped Rochester will leak internally resulting in dead spots or over-rich condition by fuel going into places it is not supposed to go.

A leaky Rochester is usually caused by the float setting being set too high, or from a problem with the float hitting the side of the bowl, or by a tiny turd between the needle and the seat allowing unending flow of fuel. Gas coming out around the throttle shaft is usually what you will see.

Just for discussion purposes, please allow me to disagree somewhat. Please don't throw rocks at me.

"A leaky Rochester is usually caused by the float setting being set too high,"
If the leaks are caused by improper float setting, why do I see so many of them leaking (see previous pictures) ?
Everybody setting them wrong?
Why don't I see a lot of pictures of the Carter YF leaking in the same manner?

"A warped Rochester won't leak gas all over the place. The warped area is above the top of the bowl."
Fuel doesn't always stay level in a bowl. Go around a curve, hit a pot hole or park on the side of a hill.

"The warped Rochester will leak internally resulting in dead spots or over-rich condition by fuel going into places it is not supposed to go."
I agree.

" Gas coming out around the throttle shaft is usually what you will see."
For overfilling the fuel bowl, I agree.

"Carter YF has a better designed float which is less likely to contact the the side of the bowl and hang up, allowing fuel to overflow."
If this is correct, the engineers at Rochester knew they had a problematic float/bowl design from 1950 to 1967 and didn't come up with a solution. My first assumptions are usually wrong so let me self correct and say the engineers did come up with a solution but for some reason they were not implemented or didn't work properly or was too expensive and the problem continues on even to today. If that is true then it just supports the general forum opinion to go with the Carter YF.

"If fuel leaks out of the top of the bowl on a curve or from hitting a pothole, then it is likely set too high."
This is the point I have trouble understanding. If I simulate a warped air horn by drilling a 1/64" hole, in the air horn, just above the fuel bowl, and the float setting is perfect (including allowances for type of fuel and needle valve construction), gas will not leak out the hole? Pot hole, curve or parked on a hill it will not leak?

No idea how to respond to that one.

When discussing carburetor "leaks", it is important to determine the meaning of the word "leak" to the original poster.

"Leak" may be anything from fuel seeping or weeping through a gasket and causing a stain over a long period of time to fuel spurting out of some hole (normally the vent) with each action of the fuel pump.

It is quite common to blame any fuel related problem on a Rochester B, if that is what is being used, and often the B is at fault; but not always. And even though I do not like the B, I don't wish to see it falsely maligned.

So:

The gasoline stain in the picture posted by the OP is probably simply a seep, which is more of a political problem than a carburetor problem. The volatility of modern fuel increases its ability to "wick". Some original carburetor gaskets (and some modern gaskets found in cheaper kits) were/are vegetable fiber. The vegetable fiber is porous, and if the retaining screws back off slightly, or even if they do not, some fuel can wick though (or around) the gasket, creating stains such as pictured. Normally, such a "leak" is so minor, the stain will never even appear to be wet; and is more of an aggravation to the enthusiast than a real problem. Warping of the air horn (common with the B) can create this situation. Filing or milling the gasket surface flat by a well-meaning but mis-informed enthusiast will make the situation worse, as the sealing ridges placed on the gasket surfaces by the manufacturer will be removed.

The most common "leak" that I see today is fuel running out beside the throttle shaft immediately after the engine is turned off. This also is a political problem, not a carburetor problem. The cause again is fuel volatility. When the engine is turned off, the inlet check valve is the fuel pump closes. This prevents fuel draining back to the fuel tank. The residual heat in the engine now heats the fuel line between the fuel pump and the carburetor. Because of fuel volatility, pressure is created in the line to a value which the combination of carburetor fuel valve and carburetor float can not withstand. A certain amount of fuel is forced past the fuel valve, raising the fuel level in the bowl. The volume is dependent on a number of variables ie ambient, length of fuel line, diameter of fuel line, and the distance of the fuel line from the engine. The additional fuel in the carburetor bowl can raise the fuel level in the bowl higher than the main discharge nozzle(s); thus fuel will drain from the bowl through the main discharge nozzle(s). As the main discharge nozzle(s) exit above the throttle plate(s), fuel will drip down to the throttle plate. What happens next is dependent upon how the owner/mechanic set the idle. If a vacuum gauge were used to adjust for the highest vacuum reading (always occurs when the throttle valve is completely closed), fuel will then run out beside the throttle shaft and drip on the manifold. If the idle was properly set, and a slight amount of clearance was available between the throttle plate and the throttle bore; then the fuel will drop down into the intake manifold, where it may create difficult starting.

The spurting leaks normally will be caused by a defective float(which would include a stuck float), defective fuel valve, or a defective fuel pump (too much pressure).

While it may be possible for a radically incorrect float setting to cause such a leak, this is unlikely. Generally, an incorrect float setting (assuming that the rebuilder is using the correct float) will cause either a mixture that is too lean or too rich.

There are other possibilities such as a blown diaphragm on a Holley type AA-1; but the majority are discussed above.

Please note the political problem (volatility) is a problem for ALL carburetors. The folks with the performance large V-8's and 1/2 inch or 5/8 inch fuel line see a lot more of these problems than folks with sixes.

The problem of fuel running by the throttle shaft may be minimized or even eliminated by installing a three line filter at the carburetor, and running a return line from the vapor port of the filter back to the fuel tank and dump in the top of the fuel tank.

However, generally the most practical way of dealing with the fuel stain pictured is a toothbrush and toothpaste

Jon.

One other comment for the OP, who asked about a rebuilt carburetor:

Jerry offered the following comment: "RUN- - - -do not walk away from a "rebuilt" carburetor. They're assembled from a bunch of mismatched bits and pieces and the odds of getting a good one are approximately equal to finding a chicken with lips."

To this I would agree, if buying a "rebuilt" carb from your FLAPS, although I use a different analogy, that of having a better chance of winning an argument with the IRS

But our hobby has specialty shops including carburetor rebuilders (this is not an advertising plug, I quit restoring carburetors due to the explosion of our rebuilding kit business some 8 years ago), that CAN correctly rebuild many carburetors. I used to offer a 5-YEAR warranty on those I personally rebuilt, and only had to honor it once (but then I was selective in which carburetors I would rebuild, and the B was not on the list )

There are a number of folks that can rebuild the various Carters (I might suggest the other Jon on this forum). I have not personally inspected his work; but I I have seen pictures and seen his comments, and would certainly give him a try if I needed a Carter rebuilt.

Maybe the moderators could start a "sticky" thread with "Jerry analogies"; they are generally good for a laugh.

Jon.

The Moderators with "the wadded panties", or one of the other ones?
Just kidding. I love all Mods regardless of undergarment condition.