My Carter B&B carburetor body is porous??

[motoMark]

I wouldn't believe it if I hadn't seen it with my own eyes.

After rebuilding the carb on my 51 Cambridge, taking plenty of time to clean and make sure everything was adjusted correctly, I installed it back on the manifold and got the old girl running. She was running real nice but I noticed a little gas where the top (air horn) attaches to the body. Ok, so I tightened the 4 screws a little more and figured I'm good. Then the gas came back again. Hmm. Did I set the float level too high? Off comes the top and double check the float - good, and look for any other potential issues. The top goes back on. Fire it up, same thing. Really weird!

I take the top back off and stare at the float and all the other parts for a while. Nothing comes to mind. I wipe all the top horizontal surfaces of the body with a shop towel and they are dry. As I'm watching, I see moisture forming on those same surfaces I just wiped down. Did it again and again with the same result. What the heck is going on? I have never seen this before. 

Any ideas or experience with this sort of thing? I'm totally perplexed.

 

[Sniper]

In order for fuel to leak thru any porosity there has to be fuel on the other side.  Which, if I am reading this correctly, is the top of the carb that is missing in your picture.

 

If that is a correct interpretation, drop your float level and see if it still happens.  I also suspect that fuel rushing in from the needle and seat area is probably spryaing ont eh backside of that missing top?

[Ivan_B]

I have two explanations: 1) there is a tiny crack somewhere (very unlikely) or 2) the gasket is letting the gas through.

To deal with the second scenario, use some sealant dressing on the gasket (I prefer permatex #2) and do not over-tighten it. Also, make sure that your level is correct. To do so, verify that the float is not leaking (dip in boiling water, watch for bubbles) and that the needle is actually shutting off the fuel flow (crank the engine with the carb top off, blow into it, etc.).

 

Also, do you still have original vacuum advance line on your carb? Would you mind posting a few pictures of how that's rounder to the distributor? 😃

Edited April 21 by Ivan_B

[motoMark]

Maybe I didn't describe the condition as clearly as I could have. If you look at the photo above, it shows gas puddling on the horizontal surface of the carb body. As you see it, without the top of the carb installed, I wipe that surface dry with a shop towel and the gas slowly reappears. You can see it as it happens. So no matter how many times I wipe it dry, the gas eventually comes back and puddles on that flat surface.

 

 

[Ivan_B]

Is it doing this when the engine is cold, as well?

[soth122003]

Are you talking about the area of the forward bold hole by the fuel inlet? If so, that looks like a fine crack and maybe that is causing a wicking action. It's something I remembered from chemistry called a Meniscus (liquid). It has to do with the attraction of a liquid to its container. This link tells about the phenomenon using water.

https://www.usgs.gov/special-topics/water-science-school/science/water-meniscus

 

Not saying this is your problem, but maybe? I'd heck the area with a magnifying glass and make sure it is or isn't a crack and go from there.

 

Joe Lee

[Ivan_B]

I do not believe that Meniscus would be high-enough to overflow over the edge like this, with the proper float level 🤔

[soth122003]

1 hour ago, Ivan_B said:

I do not believe that Meniscus would be high-enough to overflow over the edge like this, with the proper float level

 

I agree to that Ivan. Then add in a hairline crack and the float weight and fuel weight, it might be enough to slowly wick or drive the fuel up that crack, when you add in the Meniscus properties. He did say it was a slow weep that would wet the carb. Like I said, just a guess and I could be wrong, but it does make for an interesting topic.

 

Joe Lee

[desoto1939]

could the airhorn not be perfectly flat? I have seen this. Someone took a piece of flat plate glass then put emery paper down on the glass then put the bottom of the airhorn on the emery paper and then rubbed the airhorn across the paper to find a hihg spot and to get the entire airhorn perfectly flat on all the outer edges.

 

This is just a WAG  or Wild Ass Guess as they say in the Army.

 

Rich hartung

Desoto1939@aol.com

[Ivan_B]

16 minutes ago, desoto1939 said:

Could the airhorn not be perfectly flat?

I usually fix these with sealant-dressed gasket

If the fuel is actually going "upstream" I am thinking that there might be heat and/or pressure (the line between pump and carb) involved 🤔

In any event, more information from the TS will probably be useful, at this point.

[motoMark]

On 4/21/2024 at 7:50 PM, Ivan_B said:

 

Also, do you still have original vacuum advance line on your carb? Would you mind posting a few pictures of how that's rounder to the distributor? 😃

I do! Probably tomorrow I'll have time to take a few pics and will PM you.

[Ivan_B]

1 minute ago, motoMark said:

I do!

That's great news! No need to PM, you can just post them here, I am sure everyone would appreciate these, for reference 😀

[motoMark]

11 hours ago, Ivan_B said:

Is it doing this when the engine is cold, as well?

I took a quick look at it tonight (cold) and it looks a little damp but not like it was when I took the photo (warm) . Will have to investigate the conditions further.

[Kilgore47]

I have never left a carb on the engine with the top off with gas in it.  Wonder if this would happen on other similar carbs left in the same situation.  

[Ivan_B]

I was under impression that the carb was leaking from the gasket and Mark removed the top to investigate further 🤔

[motoMark]

22 hours ago, Ivan_B said:

That's great news! No need to PM, you can just post them here, I am sure everyone would appreciate these, for reference 😀

Here are some pics of the vacuum advance line routing.

[motoMark]

8 hours ago, Ivan_B said:

I was under impression that the carb was leaking from the gasket and Mark removed the top to investigate further 🤔

That is correct.

[Ivan_B]

1 hour ago, motoMark said:

Here are some pics of the vacuum advance line routing.

Thanks. Are you sure that's OEM, though? The reason I ask is because your distributor is upside-down (or did they change the setup on later models? 🤨)

 

Have you had a chance to investigate the fuel leak any further? What if you put a screw with Teflon tape into that corner hole, is the gas still accumulating over there?

[D35 Torpedo]

I think the vacuum line is suppose to follow the head around the front, not over the head. As for the fuel, perhaps parts of the alloy disolved out of the metal, leaving a sponge-like material. Or what you are seeing is vapour condensing. That's my guess. The tops of these carbs do warp easily, I usually tap the metal between the bolt holes with a small hammer, then sand it flat on a true surface. The hammer makes it so you dont have to sand as much to get it flat.

Edited April 24 by D35 Torpedo

[motoMark]

10 hours ago, Ivan_B said:

Thanks. Are you sure that's OEM, though? The reason I ask is because your distributor is upside-down (or did they change the setup on later models? 🤨)

 

Have you had a chance to investigate the fuel leak any further? What if you put a screw with Teflon tape into that corner hole, is the gas still accumulating over there?

 

As far as I know it's OEM, but not 100%. I bought the car with 29K miles on it, so I think a lot of it is original.

 

Haven't had a chance to get back into fuel leak yet but will provide updates when I can. 

[Kilgore47]

On 4/21/2024 at 6:30 PM, motoMark said:

I take the top back off and stare at the float and all the other parts for a while. Nothing comes to mind. I wipe all the top horizontal surfaces of the body with a shop towel and they are dry. As I'm watching, I see moisture forming on those same surfaces I just wiped down. Did it again and again with the same result.

 

[Dodgeb4ya]

Yeah that is the stock correct P23 vacuum advance line. It is supposed to go over the head as shown. It's never been bent out of original shape either.

Fuel line looks OE too.

Edited April 25 by Dodgeb4ya
Spell check

[Ivan_B]

1 hour ago, Dodgeb4ya said:

It is supposed to go over the head as shown.

That is correct, but the position of the distributor got me confused.

Here are a couple of the old factory production images of the 201 engine I made, for reference.

[Sniper]

15 hours ago, D35 Torpedo said:

I think the vacuum line is suppose to follow the head around the front, not over the head. As for the fuel, perhaps parts of the alloy disolved out of the metal, leaving a sponge-like material. Or what you are seeing is vapour condensing. That's my guess. The tops of these carbs do warp easily, I usually tap the metal between the bolt holes with a small hammer, then sand it flat on a true surface. The hammer makes it so you dont have to sand as much to get it flat.

 

My 51's vacuum line is routed similarly, across the head, Ian has a 40?  Odds are they changed it.

 

[Ivan_B]

Okay, they must've changed it, thanks. Sorry for hijacking the thread.

Now, let's find-out why Mark's carburetor is wetting itself 🥲 I am thinking that even if the alloy carb body became porous, somehow, (which is preposterous, in y opinion) the gas is still not expected to accumulate and puddle "upstream". The gravity does not quite work this way. A sponge drips from the bottom, it does not leak from the top. So I am thinking that there has to be a simpler explanation for the observed phenomena.