Model B Carb issues

[KMeredith87]

I have two model B carbs that's I have recently rebuilt but don't run. The castings were thoroughly cleaned out and inspected prior to painting. One has an original numbered set of jets while the other has a flow checked set from renners in it. Both seam to seal fine and don't leak fuel but won't run. The truck runs fantastic and starts with no issues with my zenith 1 on it. This is my first experience with model B carbs and am not sure what's up. Any thoughts? I'm a bit stumped...

[1930artdeco]

Are you getting fuel into the carb?

Mike

[KMeredith87]

Definitely getting fuel. Sometimes they will start but won't stay running but most of the time they won't even start

[1930artdeco]

Sounds like a either a fuel starvation or vacuum/blockage of some kind. They are not much more complicated than an A carb. I would tear it apart and make sure every passage way is clean, the fuel screen is clean, jets and reassemble.

Mike

[Marshall V. Daut]

If you didn't drill out the plugs and clean the "hidden" passageways, the carb was not truly rebuilt. The most likely culprit is in the upper casting near the idle richness needle. Drill that passage out, if you do no others. That's the one most prone to clog up. A clogged passageway here will definitely make starting and idling difficult, if not impossible, depending upon on how clogged the passageway is.
Marshall

[KMeredith87]

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Just original manifolds installed, both intake and exhaust. However, the intake has been bored out to model B dimensions.

As for the brass plug passages I have not seen replacement plugs for the model B carb so I cannot drill them out... I have gone through them with a fine wire like you would a model a zenith 1 and have found them all clear and also was able to flow wd40 through them...I know that may not mean they're completely clear but best I can do with out having new plugs...

Just opened them back up and did not find anything g out of the ordinary inside. And there is not screen like the A carb so no issue there. I also have good flow coming from the tank. Not sure what's going on but I know it's frustrating!!

[AL in NY]

There is a removable brass plug in the upper housing that has a vertical slit in it that is open to the throat of the carburetor. Careful tap it inward until it falls out and check the top of the idle passage under this plug for rust and dirt. Also, under the GAV is prone to rust also and the GAV is pressed into the lower body of the carburetor. If you haven't removed to GAV totally, the engine will never run right.

[ABento]

I was about to ask the question about the model B carb myself,I had taken a few trucks to Brooks Oregon over the weekend for the show there and in the load I took was a 1932 canopy express truck,I ended up using it for wheels to and from the motel and noticed that the carb had a cable for a choke but on inspection of the carb it looks like a GAV on it but its operated by a choke cable just to pull the choke on is that all there is on these or are they adjustable like the A's.

[Sparky]

Sorry but I have to ask, did you forget to install the venturis?

[Sparky]

Originally Posted by ABento

I was about to ask the question about the model B carb myself,I had taken a few trucks to Brooks Oregon over the weekend for the show there and in the load I took was a 1932 canopy express truck,I ended up using it for wheels to and from the motel and noticed that the carb had a cable for a choke but on inspection of the carb it looks like a GAV on it but its operated by a choke cable just to pull the choke on is that all there is on these or are they adjustable like the A's.

B carbs are normally set up just like A carbs, and have the same choke and GAV controls.

[KMeredith87]

No worries Sparky not no I did not forget them. Both carbs have an original proper sized venturi in them.

AL...didn't realize I could tap that plug out, I'll give it a shot and see what I get. However, one of my carbs is actually an early casting that does not have that plug only drilled like a model a zenith...

[Slik]

Naive question and slightly off topic - is there an advantage to running a model B carb versus a Zenith-1 ?

[Purdy Swoft]

Yes there is a slight advantage . The B carbs have a larger throat and more venturi area and a high speed circuit that cuts in at near wide open throttle. They also flow more air than any of the updraft carburetors that are commonly used on model A and B engines.

[TDO]

Right where your power jet tube goes in is a very tiny vent hole goes in on a angle . make sure it is open.

[KMeredith87]

Okay so here is an update...took them apart today and as suggested I knocked out the split brass plug and cleaned it out, rechecked the passages and reassembled. Put it on the truck and was able to get it to run and idle smooth. Everything seemed fine would Rev the engine no problems things looked good until I tried to drive it. Made it about 50 feet and it died and did not want to start again. Put the zenith one on to get it back inside, no problems...the mystery continues...

[Bob C]

Do you still have the float helper spring installed, if so maybe
that is part of the problem.

Bob

[KMeredith87]

Originally Posted by Bob C

Do you still have the float helper spring installed, if so maybe
that is part of the problem.

Bob

No spring installed; just the baffle and float....

[Sparky]

I'm no expert, but I also have two B carbs, one of which I am currently running on my speedster. The first one I got ran great, I didn't need to do anything to it other than replace the gaskets. I was able to get the second one at a great price, and although it looked very nice, it ran like crap; the engine started but wouldn't idle and did not accelerate smoothly. When I carefully compared it to my original good one, I found two problems:

1. The compensator jet was not marked, and although it appeared to be the correct drill size, it was actually a jet meant for the Zenith A. The difference is that the correct B jet is shorter in length. So I got an original B jet (marked "18") and that fixed the acceleration issue.

2. The idle air screw had no affect on the idle even when completely closed. I found that the screw threads were either rusted or dirty near the bottom of the hole so the needle was not fully seating even though the screw stopped turning. Chasing the threads with a jet tap fixed that issue.

Also, neither of my carbs have a float return spring.

Other than the "power valve" circuit they work just the same as the Zenith A. One thing you could experiment with is swapping the tops and bottoms.

[KMeredith87]

I'll give it a shot swapping bottoms out as the one has all original jets while the other has flowed jets from renners (I've heard nothing but good things about them, no complaints here but who knows). I get adjustment from my air mixture screw so no problems there. I actually had it running great until I tried to drive it off...

[Sparky]

I'd take a look at the compensator and cap jets and passages.

Have you seen Vince Falter's web pages about the Model B? You may find some more help there:

www.fordgarage.com

[TDO]

I also run a model B carb. that I rebuilt with Renners flow tested jets. Mine runs great. Un like the A model I never use the GAV just leave it closed. I did put in the stainless steel power jet tubes I bought from e-bay.

[KMeredith87]

I trust renners and y he carb that I got running had their jets in it but it won't run once a load is out on it. I also have the stainless power tube but I did not install it as the brass one seems fine currently.

Sparky, I actually check the Ford garage before starting this thread. Lots of info about the carb but not a whole lot about rebuild that I saw. I keep fiddling with it and hopefully get it figured out.

[Brian T]

Originally Posted by KMeredith87

I have two model B carbs that's I have recently rebuilt but don't run. The castings were thoroughly cleaned out and inspected prior to painting. One has an original numbered set of jets while the other has a flow checked set from renners in it. Both seam to seal fine and don't leak fuel but won't run. The truck runs fantastic and starts with no issues with my zenith 1 on it. This is my first experience with model B carbs and am not sure what's up. Any thoughts? I'm a bit stumped...

Seems odd that you have 2 B carbs with the same problem, the symptoms act as if the float valve is stuck shut, run a while then stop, pulling the choke it may attempt to run.

It is my understanding the only float valve available for a B carb is the Grose jet (ball valve) noted for sticking closed when the engine is not running, we used them in the 70s to cure flooding on import cars with opposite results.

My truck runs very well with the B carb, however I have had to unstick the valve a few times, my worst experience was having the problem occur while driving, I posted here asking if there was a conventional valve available, Renners say that is all that's available.

I did replace it but later the same symptoms occurred, so I ask again is there a standard type needle float valve available that fits the B carb, if someone has one used or otherwise please PM, hope this will help with the above post.

[KMeredith87]

I'm fighting through the problems....got it to run and drive but once I hit 50-52ish it bogs down pretty bad and wants to stall and idles a little strange. On the up side the engine seems to run smoother with this carb just need to get it running right.

As for the float valve...I have an original brass seat and needle similar to the A's. I took it apart and cleaned and polished the needle and seat together using baking soda and toothpaste as suggested on other post in the past. This method worked well for me and seals well. Also, I've definitely not ruled out myself being part of the cause seeing as you said I have two that seem to being doing the same thing. I've rebuilt carbs in the past and haven't had a problem but the B carb is new to me. Getting to the point that I'm half tempted to send it to renners and let them fix it for me!

[c. sefton]

Are you using different fuel lines from "a" carb to "b" carb set up? Maybe your "b" fuel line is going to far into "b" carb, restricting flow.

[afuncar]

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I tried a B carb on my A, every corner it would stall no matter what I tried, thought I checked everything no better. Finally found the problem, the float was leaking!

[tiger.1000]

Meredith,

Out of interest, what procedure are you using to start from cold? Model B carbs have in the past driven me nuts !

On my 32 Model B to start from cold I pull the choke out and turn the choke anti-clockwise about 2 full turns for cold start. This opens the GAV. Once started I then turn the choke cable clock-wise leaving it open about 1/2 turn . I find that if I try to drive with the GAV closed the car is reluctant to accelerate smoothly.

Reams have been written on this subject and it seems no two B carbs are the same and no two Model B cars have the same starting/driving procedure.

After a close encounter with the shrink I sent mine to Dave Renner. He is the man.

[KMeredith87]

Tiger,
I've honestly tried about every different starting method with them to get it to run right and no real luck one way or another. With the zenith 1 installed the truck will start up on typical day on a cold motor with no choke with in about 10 seconds or so...I think I will have to pick up a model B carb book and see what it has to say and if worst comes to be I'll send it in to renners!

[tiger.1000]

Meredith,

Send me a PM including your email address and I will forward you an email that Dave Renner sent me. It includes two diagrams; one showing an exploded section of the B Zenith together with the procedure for checking all of the jets and passageways.

In the meantime if I can work out how to post them on the thread I will do that but I am computer ILLITERATE !

!

[tiger.1000]

Meredith,

Hope you can read this? Dave Renner's procedure for testing B Zenith.

Good luck !

[Purdy Swoft]

tiger 1000 is correct. I have run and rebuilt my own model B carbs for years. You do need to open up the GAV for cold starts or they will hesitate and quit. Try opening the GAV untill it will take the gas without hesitation. It only takes a brief warm up. when the engine begins to lope, reach over and close the GAV and you should be good to go. I use original jets and have never needed to remove a passage plug. A small wire carburetor cleaner and compressed air has always worked for me. I buy swap meet carbs and do my own.

[KMeredith87]

Thank for the info tiger! And purdy that's my goal eventually to run dual Bs like you have but have issues with just one right now. I was able to get it to idle well and once driven a mile or so the idle became rough and acted like it wanted to die then would bog down badly around 45-50 or so. Definitely want to be able to do my own as unforunately the availability of people who can do it for you is slowly decreasing...

[tiger.1000]

Meredith.....here's a silly question.....have you checked your condenser ? They can play up when warm and create mis-fires and then die on you , then come back to life when cold.

[KMeredith87]

I'm actually running one of bubba's ignition centrifugal advance Mallory's...no problems with the distributor as I just installed it a couple weeks ago (fantastic distributor for those who are curious) and also the truck with run just fine with my zenith one on it and can and will whit 65-70...

[Marshall V. Daut]

I just got a Model B carb working correctly the other day that I hadn't run in 15 years. All passages were clear and everything checked out before mounting it on a friend's car. Yet, on occasion and not every time, the engine would start to sputter, idle poorly and then gas would start coming out of the throat. I lowered the float some and changed needle & seats, but still the intermittent problem existed. The float had two small solder repairs, but based on its use for 10 years prior to going into storage, I felt the float was o.k. However, after disassembly and fooling around with the carb for about the 100th time, I shook the float and sure enough! There was gas inside. Apparently another small leak had developed and gas was getting inside the float, but not completely filling it. What was happening was when I disassembled the carb and laid parts on the ground, gas must have dribbled back out of the float so that it would operate o.k. for a while before just enough gas seeped in to cause it to sink. That caused the misfiring and eventual gas running out. Disassembling the carb each time, who would notice gas dribbling out of the float amid all the gas on the ground from the bowl? Anyway, a new float from Renner's Corner solved the problem and the engine runs great.
I know you said your float was good, but check it again. They are so light-weight that even with some gas inside, it's hard to tell for sure unless you shake it and listen for sloshing inside.
Model B carbs are GREAT when dialed in, as they all can be if proper rebuilding procedures and CORRECT parts are used. Installing a rebuild kit is only the first step. Each jet must be checked for size and length. These kits are made of parts that are close, but not exactly correct for Model A and B Zenith carbs. They often come from tractor carb kits. Unless the jets have been flow-checked and the lengths measured, its a cr*ps shoot if the carb will function properly. Don't give up on these B carbs yet! They CAN be made to work the way they were designed.
By the way, to get around the carb being mounted at an angle on the bored-out Model A carb, I ground the shafts of the mounting bolts in the area where they go through the intake manifold flange. That allowed the carb to be rotated enough to line up nicely with the choke rod = no more binding. This method costs nothing and does not compromise the integrity of the mounting bolts. There's still plenty of meat left on the shanks to hold a one pound carb!
Marshall

[KMeredith87]

Marshall, I will check my float again as who knows what has happened. When I checked it initially I kept it submerged in water for a couple days and then submerged in cleaner for a couple more and found no leaks and always came right back to the top of whatever it was in. As for my jets...they are all proper jets flow check by renners though I do also have an original set that I am not currently using. When I have it on the truck and running it seems to have the truck running smoother, that is until all hell breaks loose anyway!

[Tom Wesenberg]

Shake the float to see if it has any gas inside. If not, then dip it in hot water and any pin holes will show bubbles right away.

[KMeredith87]

I double checked the float today...didn't hear any fuel inside of it so I brought inside and put in hot water as Tom suggested and no leaks. Almost wish there was at this point...does anyone know exactly what the float high should be at on a B carb? Right now I just have it set similar to how I would a zenith one and just ensured the float seals the seat closed when completely vertical...

[jim1932]

I am no expert, but can you post a photo of the carb opened up? I had one I forgot to put a power tube back in.... since oyu did both of them maybe there is a mistake someone can spot.

[KMeredith87]

I'm up for anything at this point. Don't have the best pictures at the moment but here is one I took yesterday when speaking with someone else about it. There is no spring on the float, new flow tested jets, no leaks in the float, all passages clear as per Renners instructions, new power tube. Think that about covers everything...

[AL in NY]

I don't the removable venturi. Either it not pictured or you don't have one.

[KMeredith87]

Sorry, forgot about that! I do have one and it has been in but it's not pictured.

[TDO]

FAR AS THE FLOAT LEVEL, I SET MY B FLOAT SAME AS THE A FLOAT. Mine runs great.

[1930artdeco]

I have run a B carb on my car just like yours, original jets etc. I however, do not have the brass shim that you have under the float. Sounds like your float is good, try removing that shim. It may be binding the float up.

Mike

[AL in NY]

I agree with 1930artdeco, try removing the baffle under the float. When I first installed my Zeinth B, I couldn't get it to work reliably with the baffle installed.

[tbirdtbird]

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starving for gas.
check GAV circuit carefully

[AL in NY]

As I said in post #8, the pressed in GAV needs to be removed because the spring and the washer under it tend to rust. And because of the spring, that area is almost impossible to clean if rust is present.

[KMeredith87]

I haven't had the chance to remove the shim and give it a shot yet but that will be one of the next test.

AL, I don't have the proper tools to remove and reinstall the GAV circuit. Any suggestions on how to possibly remove the. And reinstall without messing it up? I actually do have a new spring and washer for it but no way to install. What about filling the bowl with evaporust?

[Purdy Swoft]

Artdeco makes a good point in post #46 . I don't run the lower shim in my B carbs. Another possibility that I don't think has been mentioned is the possibility that the needle valve could be sticking. I've had problems with viton tipped needles sticking closed. Ethanol fuel contributes to this problem. I notice that the high speed jet that presses into the upper housing is missing. Without the high speed jet, the B carb would probably not perform much if any better than a model A Zenith carb. I've made this jet by turning the nut off a model A idle jet and shorting the tube to proper length. The diameter is the same.

[KMeredith87]

Purdy, the power jet is there, it's a stainless replacement tube instead of the brass. I'll try removing the shim for sure but right now it sounds like a May be having a problem in the GAV circut. My needle valve is actually an original I took apart and polished for a tight seal and seems to be working fine right now. I too have had problems with the viton seals and won't use them anymore, not worth the hassle to me.

[Purdy Swoft]

Sorry, I see it now. Don't know how I missed it.

[Ron in Quincy]

Unless you are running a fuel pump, the baffle and spring are not necessary. The baffle and spring only appear on the 33-34 B carbs; the 32 B carb uses a round float with no baffle and spring.

Ron

Another way to identify a 33-34 lower bowl is a cast baffle in the bowl 11/16" down from the mounting surface on the passenger side of the bowl.

[AL in NY]

To make the puller for the dash-controlled needle housing you need to obtain a 1/4 x 24 die. You won't find it at your local hardware store but industrial supply houses carry them. That's the thread on the GAV adjusting needle. Kmeredith87, I think you would be wise to purchase a copy of Gordon Biggars book "Restoring The Model "A" and "B" Carburetor - The "Rex" Reheis Way". I saw your earlier post on not being able to find the correct bass plugs, so you didn't remove them for your rebuild. Biggars books tells you how to fabricate plugs. But there is another way. You can drill and tap the plug holes and then insert set screws with a thread sealer applied. You are not building a fine point car, so who cares what the plugs are made from if the carburetor functions correctly after it's rebuilt.

[Giles]

Originally Posted by AL in NY

There is a removable brass plug in the upper housing that has a vertical slit in it that is open to the throat of the carburetor. Careful tap it inward until it falls out and check the top of the idle passage under this plug for rust and dirt...

Hi Al, and everyone,

I have just removed and cleaned this plug in my model B carb. I noticed that as well as having the vertical slit and a passage drilled sideways through the plug, there is a tiny hole on the outside end of the plug (ie opposite end to the slit). This does NOT, however go all the way in till it meets the crossways hole. It is not blocked - it clearly never went all the way.

My question is simply: should this hole meet the crossways one? (In other words, have I got a faulty plug?) If it doesn't, what is it there for, since it doesn't connect with anything?

Thoughts, anyone?

Best wishes and thanks, Giles

[AL in NY]

Giles, I believe that "hole" is just a punch mark and it doesn't go through to the vertical passage.

[Giles]

thanks Al - now I can relax!

[JRN1967]

Originally Posted by AL in NY

There is a removable brass plug in the upper housing that has a vertical slit in it that is open to the throat of the carburetor. Careful tap it inward until it falls out and check the top of the idle passage under this plug for rust and dirt. Also, under the GAV is prone to rust also and the GAV is pressed into the lower body of the carburetor. If you haven't removed to GAV totally, the engine will never run right.

Al, This winter I bought a rebuild kit for my B carb. When I installed the carb it ran like it was starving for gas. It also stalled at quick stops, which exactly what it was designed not to do.

I tried adjusting the float level many times and removed the baffle. I put it on the shelf and almost forgot about it. Then I picked up a 31 Sport Coupe that was missing the carb (and some other parts), so I needed to get this carb working. Through a search I stumbled onto your suggestion here about removing the brass plug with the vertical slit.

I just wanted to say thanks, because now the B carb runs great. It's so good that I'm going to put it on my driver.

John

[rich40701]

When the brass plug with the vertical slit is tapped do you leave it out. I have had the B carburetor on my A on and off 3 or 4 times now and it starts really easy but the idle is very erratic. One minute it will be idling great and the next it won't idle unless you increase throttle. Additionally when I first put new jets in it seemed to have more power but leaked fuel so I took it back apart and adjusted the float and took all the jets out to make sure nothing was leaking. After I put it back together I still have poor and erratic idle but now loosing power at top end. The only good thing is it no longer leaks gas.

[RENNERS CORNER]

I make all the plugs for the model B Zenith but that's ridiculous to drill them out if the passages check good with compressed air there is absolutely no reason to drill those plugs.
When they were brand new they operated perfectly, jets are not the reason for your issues.
Over the years people have mixed matched parts you cannot mix parts from the B1 zenith and the B2 zenith without knowing what you are doing. See photo attached of throttle plate with notch as an example of a part that you cannot enter change.
I have attached diagrams for the model A & B Zeniths and a checklist for going through all of the passages and circuits with a rubber tipped blow gun.

[RENNERS CORNER]

The hole on the outside of the plug on the outside of the carburetor was a manufacturing hole for orienting the plug so the slot was straight up and down. That plug is called an idle aperture and that's where all of your fuel for the idle circuit enters the throttle bore.

[RENNERS CORNER]

The float and baffle work independently from each other and one should never affect the other if it's installed correctly. Attached is a photo of a new old stock B-2 zenith and how the assembly should look. The spring is used only with the fuel pump, when gravity fed it should be removed.

[31a]

If you rur a ab carb on an A intake you need to have it ported to get the best performance out of the B or use a B intake.

[old31]

Will a model B intake bolt up to an A with no changes?