The Stovebolt Site Forums The Shop Area Engine Shop carb leak on '46 1/2-ton 235

My recently acquired 46 1/2 ton has a 235 in it. Installed by the previous owner. I bought it, got it running and it runs great with the exception of one thing. The carb leaks fuel intermittently down the side of the body from somewhere... All fasteners are tight. I took it off to clean and inspect it and found a lot of fuel pooled down in the intake manifold! What would cause that? The carb is an aftermarket remanufactured unit with no markings and was a recent addition. Any ideas???
Bob

Float level too high
Fuel pressure too high
Carb incorrectly assembled

Can you post pics of the carb and/or provide the tag info off it? We could give better feedback with more details.

Here ya go. No tag or numbers to be found.

It looks like some sort of variation of a Carter YF.

Rebuilt 8 years ago but maybe it sat around not being driven and gunked up inside.

Carbking will be along to identify it for you and get you the proper rebuild kit.

Yes Carbking will be able to id it. That is similar to a Carter YF I had that was used on Chevy 194 and 230 pickups. Since it was a manual choke, I went through it and found it to be in decent shape. Comparing it to the YF2100s, the air passages, jets, metering rod, etc were fairly close. It didn't do badly on the 235. In fact it ran very well, but I prefer an auto choke. The one I had was somewhat different however. The throttle body was cast iron and didn't have the vacuum port. I think the number was YF4145S, and I think it was for a 1965-ish Chevy pickup.

Your problem might also be a cracked/ruptured diaphragm. If the diaphragm is compromised, it wont seal, will allow fuel to leak from the float bowl into the vacuum chamber below it and if that happens it will be sucked right into the manifold and also will dribble and leak along the area where the float bowl connects to the throttle body. It will definitely pool in the manifold and will run rich. A couple or three years ago I showed how to make a little gizmo out of a flat piece of wood and some 320 wet/dry sandpaper that will enable you to make the diaphragm bonnet nice and flat. They can be warped by ham fisted repair people.

Jon I’ll be happy just to identify the carb for a correct kit. All of my symptoms sound like what you encountered in the past. I feel like it’s a Chinese knockoff since there are zero markings or numbers on it. This engine has been identified as a 1957. So I may end up searching for an old original that is rebuildable.

Carbking cannot identify the Chinese imitations, and makes no parts for them.

I would suggest looking for an original.

Jon

Oh gee. Looking at that throttle body I was afraid of that but was hoping it wasn't so. Good luck. A 1957 235 will be happy with a YF3211S...but that is an auto-choke model and some folks here don't like those. Personally I've preferred them since around 1965.

I’ve acquired a carter YF and a rebuild kit. It doesn’t have any ports for vacuum options such as wipers and vacuum advance like the Chinese carb has.

Vacuum for the wipers is typically taken from the intake manifold.

There should be a vacuum port in the throttle body to use for the distributor.

If you have no hole in your intake:

For decades, G.M. used a hollow carburetor stud for a vacuum port. These are being reproduced. The stud may be used for wiper vacuum.

Jon

Here is a picture of the vacuum advance port on a YF2100s carb. Your’s should be similar. It’s 1/8” NPT (female pipe thread).

Got it, I see that on my throttle body. Thank you! I just have to get the float adjustment set tomorrow, reassemble, install and try it out. Comes at a great time, my 2006 crew cab silverado was stolen today and it's my daily driver. Or was anyway. So Tina, the 46 truck will have to take up the slack for the time being.

So the Carter carb has been rebuilt, float level set to specs and installed. Fired it up and still have the same issue. Too much fuel pushing past the float. I installed a new fuel pressure regulator and no change. Even with it set at 1psi.
Anybody????

It sounds like the float valve is not seating properly. After replacing the float valve, I blow thru the inlet (using just my mouth) and gently raise and drop the float to see it is will operate properly (seal the air off and on). You can use a fitting and a piece of tubing to make it more sanitary if you wish. Do not use compressed air, as you are trying to stop only 4 lbs. of pressure.

Carter used a spring-loaded fuel valve in the YF carbs built for Chevrolet, with an orifice of about .081.

Carter used a standard fuel valve in the YF carbs built for the Ford 300 CID with an orifice of about .101.

When your FLAPS still did a decent business in carburetor rebuilding kits some 30 years or so ago, out of a hundred YF kits sold, they sold maybe 99 kits for Ford, and 1 for Chevrolet (remember, the YF is aftermarket for Chevrolet). Since "one size fits all", guess which fuel valve comes in the FLAPS kit?

If you got a kit from us, or if someone else makes a kit with the correct spring-loaded valve of which I am unaware, which you acquired; the float adjustment with the spring-loaded valve is made with the weight of the float resting (NOT pushed down with your finger) on the fuel valve.

Inline dial-style regulators with no bypass, and no return line are quite useful if you have a strong right arm (or left) and a rabbit problem in your garden!

For a fuel regulator to work properly, it requires a bypass with a return line.

Jon

Jon I purchased the kit from NAPA. Float level was made with the float resting, no finger pressure. Incidentally the Chinese carb that was on the engine when I bought it was having the same issue. That’s the reason we are having this discussion.
$89 for the rebuild kit on this Carter and I still have the same issue. Where would I go from here???

I won't discuss the Chinese carb, there really is no reason to do so, and insufficient information to do so even if there was a reason. But there is sufficient documentation and parts existing that your YF CAN be fixed.

Do you remember if the fuel valve was spring loaded or solid?

And most would never think to measure the fuel valve seat orifice, but I would suggest this is your next step.

The spring loaded valve has a hole drilled in the end of the valve opposite the point. A small spring is inserted in the hole, and a small metal pin resembling a golf tee is then inserted into the center of the spring.

Jon

Jon the kit came with two options. The one I chose resembled the parts that came out of the body I was rebuilding. In the picture below is the other option. I installed the one without the spring loaded valve.
Also I felt that while the Chinese carb is out of the picture, the fact that both carbs exhibit the same issue is pertinent to solving the problem wouldn’t you agree?
Anyway, the valve seat orifice in the one installed is larger than the one I didn’t use still in the bag.

Your in good hands now, so I’m going to bench myself and let the pro take over. I will be following this thread.

Bob - the valve pictured is the currently available spring-loaded valve for marine AFB and AVS 4-barrels. It has an orifice of 0.092, which is large for the Chevrolet YF. If this one is too large and the one you used is larger, then..........................

History:

Carter developed the spring-loaded fuel valve in the 1930's for off-road and marine application. The spring tends to make life easier on the float under extreme conditions (bow of the boat hitting waves, or a truck tire hitting large holes, being on the side of a hill, etc.). If your truck is used primarily on road, then the spring-loaded valve does not enjoy a large advantage over the solid valve (on second thought, the pot-holes in the streets around here might be an advertisement for the spring-loaded valve )

I saw a tourist sitting in his lawn chair on the side of one of our city streets after a rain fishing in one of the pot-holes!

Seriously, the orifice size for non marine or off-road is more important than the spring.

The float in the carburetor has a certain buoyancy, and because of this buoyancy, the float will exert a certain pressure to withstand the input fuel pressure. The larger the fuel valve orifice, the less inlet pressure can be held with the same float.

As to the Chinese carburetor and your YF exhibiting the same issues? Honestly, there is insufficient data available on the Chinese carburetor to confirm or deny that assertion. Maybe yes, maybe no.

Jon

Alright we’ll what I’ve gleaned from this is to see if I can just buy a valve with a smaller orifice.

Carter 25-239s

Jon

Jon using that part number I’m not seeing anything. Is that something you carry or do you have a business reference for it?

PM sent

Jon