Model B Carb. on a Model A - pros & cons ?

[DougVieyra]

With their vast experience and years of knowledge - I thought I would ask Ford Barn Forum contributors their ideas and input on the question:

If I use a standard (stock) Model A intake manifold, what would be the "pluses" and the "Minuses" of using a Ford Model B carburetor ?

[Tom Wesenberg]

Not enough to gain to make it worth the switch. Model B carbs don't seem to stall at stops like many A carbs do.

[Mike V. Florida]

No pluses. Bore out the intake and then you will have something.


Intake Manifold Enlargement

[Charlie Stephens]

Originally Posted by Mike V. Florida

No pluses. Bore out the intake and then you will have something.


Intake Manifold Enlargement

Mike,
Is there any reason to bore an A intake instead of using a B intake?

Charlie Stephens

[Mike V. Florida]

Originally Posted by Charlie Stephens

Mike,
Is there any reason to bore an A intake instead of using a B intake?

Charlie Stephens

Most A owners already have the A manifold.

If one were to do a search for Model A and Model B intakes the A intake is far more available.

[H. L. Chauvin]

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Hi Doug,

FWIW:

In many cases, most Model A owners have lots of respect for "all" of the "different" Model T/A/B opinions of others, mainly because these opinions are for the most part based on "real" past experiences.

And, almost every Model A/B question just never has one (1) cut and dry response.

I think that after 80+ years or so, some could possibly find a B carburetor on E-bay that someone found under his neighbors hen house, buy it, and wonder why they get 10 MPG less than the A carburetor someone found on an abandon turkey farm under an out-house.

Intake size as mentioned often can affect performance, "especially" at higher speeds when one can hear the carburetor intake whistling.

I used to talk to Mr. Charlie Yapp often years ago, and in his "Journal of Secrets of Speed Society", he listed very interesting and informative articles written by Henry Miller, Jim Brierly, Murray Fahnestock, Paul Moller, Bob Rentz, Ron Kelley, Urb Stair, and several Model A "improvement" articles from the 1930's Popular Mechanics and Popular Science.

Mr. Yapp also wrote this years ago:

"When Ford redesigned their four cylinder engine, for the third time , (T, A & B), one of many changes incorporated to increase horsepower was the new Zenith updraft carburetor. This cast iron carb has larger air intake, and exit ports, a larger venture, and most importantly, a power jet that kicks in at higher speed."

The B has an intake of 1-1/8" diameter in lieu of the A's 1" diameter ..... a mere 1/8" difference .... but wait ...... what happens when Mr. Pi x and Mr. R-square attacks this 1/8" ..... i.e., 3.14 x .5 x .5 = .785 sq. ins. for the A intake; vs 3.14 x .563 x .563 = .995 sq. ins for the B intake; where .995/.785 = over a 26% increase in a B carburetor's intake's "area" for the engine's fuel mixture flow.

Existing conditions of 80+ year old A/B carburetors mixed with repro and original jets can also result in many different experiences and many varying opinions.

At higher speeds, a properly re-built B ...... or an original B right out of the box should perform better.

[2manycars]

I have a B carb on my tudor, and the increase in performance was noticable, even after having several A Zeniths and a few Tillies on the car over the last 49 years. It also does not faulter during a quick stop.

[oldguy41]

I have a B Carb on my speedest, along with a B Head. I had a local machine shop bore out the A manifold. it runs well and stops well. A well adjusted A card was replaced. How you drive and how you adjust your system will provide a increase in horse power. The B intake manifolds I found were to costly for my project. It only cost 25.00 for the bore.

[Terry, NJ]

I've bored out a few manifolds in my time and I'm a believer in the bored A manifold with the B carburetor. The only additions I can make are That I prefer a 1 9/32" (1.281") drill.
If you look at the thickness of the casting, you'll notice it's walls are getting mighty thin.Then you're going to drill them out a little further? I like a 1.281 that cuts a little oversize and the polish it lightly, taking a little more at the bottom. Why? Because of the Bertoli's venturi principal. Don't "Bellmouth" the top of the bore. Progressively enlarge it as you go down to the bottom. Then turn the manifold around and polish the other ends, those that go to the block. Putting your finger up the the holes, you can feel many casting flaws that will impede the flow of the gas/air mixture. Polish these out so the sides are smooth. Curiously, you don't need a mirror finish, just smooth. There is a big "Debate" going on, in which one side says it must be mirror quality and the other says that slightly rough walls (Very small scratches) help with the atomization and mixing of the gas/air. Who Knows? Both sides have their reasons. By tests, this should gain you about 3-4 HP, considering that the Mod A engine is 40 HP, that can mean about a 10 % increase. Definitely worth the effort!
Terry

[Fred K-OR]

I had a B carb on my huckster and it seemed to use more gas that the A carb I now have on it. Did not notice any difference in performance but the manifold was standard.

[H. L. Chauvin]

FWIW: B Carbs on Marine Engines

In the 1930's, outboard motors had antiquated 1930's varnish covered wire coils that would soften and short out with heat. Immediate re-starting of old early 1930's outboard motors was often difficult, where one had to allow the coil(s) to cool prior to re-starting.

Few fishermen, sports and/or commercial, would tolerate paddling home in the dark, or worse, in rain storms, so it became popular to install far more dependable 4 cylinder Ford engines in fishing boats.

Then, sports fishermen usually traveled at two (2) speeds ....... wide open ..... to and from their favorite fishing spot ........ and ..... stop .... to fish.

It did not take long to learn that with a four cylinder Ford A/B engine, at "wide open", a B carburetor could attain higher speeds on an A or a B engine.

My all original B carb, with original jets, came from my Uncle's B marine inboard engine.

As mentioned on a previous post, I get 20 MPG with this "unrestored" original B carb on my Town Sedan ..... never tested my Town Sedan MPG with my rebuilt A Zenith, my Tillotson, or my Sears Marvel.

[msmaron]

I have one for the last year and a half and do have a bored out manifold and love the B, i see better gas milage, better pickup, more top end speed and easy to maintain, NOW i do also run a B distributor with the built in advance and i am sure that also makes a difference. Bought them both from Renners Corner...

[H. L. Chauvin]

Per Mr. Terry's post #9, in calling Mr. Ron Kelley and Mr. Charles Yapp years ago, according Mr. Kelley's very detailed experiments in documenting engine performance dynamometer tests, they agreed if one wants a single, very inexpensive increase in HP, just remove the rough cast iron insides and sharp corners of the intake and exhaust ports, which will allow more and faster velocity flow of the "already" atomized fuel.

In my opinion, further mixture and slowing fuel velocity with rough friction surfaces inside engine ports is not required ....... e.g., a Model A/B carburetor works like our old Flit Gun ..... once the Flit liquid is atomized, one does not need to stir and beat up this mixture with a boat paddle to kill mosquitoes on a distant wall.

[TDO]

I do like the B carb. It doesn't stall at sudden stop. Also I never use the GAV, while starting or out on the road. I do have flow tested jets from Renner's.

[H. L. Chauvin]

FWIW: Hope this helps if one has a malfunctioning early B-1 Carburetor, (or even an A carburetor), flooding at instant stops:

I have what Mr. Paul Moller referred to in Chapter 9 of his Volume 2 Book as the earlier B-1 Model B carburetor, with the "drum shaped float" which used to flood the vehicle's engine and cause the engine to stall upon sudden stops, similar to that of the round bottom Zenith A carburetor.

Stalling immediately stopped once and for all ........ but, after following Mr. Rex Reheis's recommendation, i.e., in his book, to adjust the A or B carburetor float such that the fuel level in the carburetor bowl is 5/16" lower than that of Ford's recommendation.

[Kevin in NJ]

The 30 fordor I had came with a B carb.

Was really snappy, the car like to run. Yes I ran it 55 all the time, it was happy.

I didn't like having a B carb so I put a well rebuilt A carb on and I could not find a difference.

I did not keep track of fuel miles on that car. Just stepped on the gas and went.

[Terry, NJ]

Henry, I wish I had detailed results of my own! That not being the case, I recalled someone posting Vince Falter's (I think it was) testing that produced the numbers. There is every reason for the B carb. to be superior to the A carb.
1) as you said before, The 1/8" larger dia. throat that allows approximately 25% more air more into the engine. This has to be worth something.
2) The last evolution (B-3 ?) that has the rectangular float, mounted 90deg. to the longitudinal axis of the car certainly corrects the problem of of stalling at stops.
3) The acceleration jet. I believe the addition allows for leaner running.
If someone knows about these tests and results, I would appreciate if they could post the link. I think it was Vince Falter, maybe I'm wrong.
Terry

Originally Posted by H. L. Chauvin

Per Mr. Terry's post #9, in calling Mr. Ron Kelley and Mr. Charles Yapp years ago, according Mr. Kelley's very detailed experiments in documenting engine performance dynamometer tests, they agreed if one wants a single, very inexpensive increase in HP, just remove the rough cast iron insides and sharp corners of the intake and exhaust ports, which will allow more and faster velocity flow of the "already" atomized fuel.

In my opinion, further mixture and slowing fuel velocity with rough friction surfaces inside engine ports is not required ....... e.g., a Model A/B carburetor works like our old Flit Gun ..... once the Flit liquid is atomized, one does not need to stir and beat up this mixture with a boat paddle to kill mosquitoes on a distant wall.

[Bruce,Upstate NY]

I'm intending to change from A to B carb and manifold. I have two B manifolds, one with vacuum port at the rear and the other a large one at the front. Who knows why?

[Brian T]

Bruce,
The manifold with the vacuum port at the front (which is what I have) was intended to supply a vacuum operated clutch, the idea was scrapped, the next version a small port was in the rear, both manifolds will work Ok.
Go to Vince Falters Fordgarage, much to learn from it.

[jm29henry]

Model,A's were built,with a zenith if it is a good carb nothing will run and idle better it was specially design for your car

[Terry, NJ]

The test results I was referring to were posted more than a year ago. Thanks for posting the Vince Falter, Ford garage. I went there and could not find what I was referring to, so once again, my memory has failed! Nothing new about that! Thinking about it, I seem to recall it was someone in Texas.
The reason I referred to the B3 carb was that was the one with the most refinements, being the last evolution before the engine was discontinued. I realize that Ford saw they had problem with stalling in the old A carb. and refined it in their new B carb.
Terry

Originally Posted by forever4

Just for clarification, I did not post any test results from the B carb.

Also it should be noted that all versions of the B carb have the float hinged the same, 90 degrees different than the Model A Zenith float.

This is true regardless of the style/shape of the B float. The B float hinge pin is aligned with the fore-aft axis of the car.

[john charlton]

The "One Ton " AA truck was built at the Dagenham England plant into 1936 . These trucks were fitted with the Dagenham built model B engine and carburetor. Initially they were fitted with the RHD model A inlet manifold as it has the "peg" on which the manual advance/retard pivot is situated . These inlet manifolds were stock and not bored out so the 1/16" lip existed from the factory . In practise the setup worked just fine .I have this combination in my 1930 cabriolet . The extra gas flow given by boring out the manifold to suit the B carburetor only holds good at full throttle with your foot hard down . In normal driving the partially open throttle plate obstrucks the flow far more than the bore mismatch . My theory is the "lip" causes more turbulence and better gas atomisation so better combustion . Ford was happy with this setup but the later trucks were fitted with the "B" automatic advance/retard so the "A" inlet manifold was deleted .

John in we will soon get the bad weather from NE USA in Suffolk County England .

[DougVieyra]

Charlie Stephens, post #4: "Is there any reason to bore an A intake instead of using a B intake?"
_______________________________

While talking about 'A' vs. 'B' intake manifold, let's not forget that while the 'B' manifold does have bigger orifices to better utilize the larger 'B' intake, the mounting flange on the manifold is a slightly different angle than the 'A', and will not let the GAV rod to operate.

It is true that there is a kit currently available to correct/adjust the 'B' flange mounting of the carburetor, so this off-set angle can be corrected.

And too, the 'B' intake manifold has a flat top (and sometimes some 'bumps') that define it as a 'B' intake. So for those who wish to avoid having to buy a kit to get a correct angle for the GAV rod, and who wish for a more stock looking manifold, the stock 'A' manifold (properly bored out) will be a better choice for some. Others might like the definitive look of the 'B' manifold, mated to a 'B' carburetor, because it helps bring recognition to the fact that the engine has been 'hopped up some'.

[Terry, NJ]

John, I have over 25" (around 67 CM, I think)on the ground here in Bucks Co. Pennsylvania. Fox weather just reported that parts of New Jersey (to the east of us) have 33" Temperature was 15 to 18 deg. F. It's a beautiful day! Sun's shining, birds are singing, a full moon, going down in the west! What more could you want? (And me with a Case 580 E backhoe, snicker)
Terry

John in we will soon get the bad weather from NE USA in Suffolk County England .[/QUOTE]

[Jwilli]

I have a B carb on the 29 and a Tilly on the 30. Both work very well.

[Sparky]

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Originally Posted by Terry, NJ

Henry, I wish I had detailed results of my own! That not being the case, I recalled someone posting Vince Falter's (I think it was) testing that produced the numbers. There is every reason for the B carb. to be superior to the A carb.
1) as you said before, The 1/8" larger dia. throat that allows approximately 25% more air more into the engine. This has to be worth something.
2) The last evolution (B-3 ?) that has the rectangular float, mounted 90deg. to the longitudinal axis of the car certainly corrects the problem of of stalling at stops.
3) The acceleration jet. I believe the addition allows for leaner running.
If someone knows about these tests and results, I would appreciate if they could post the link. I think it was Vince Falter, maybe I'm wrong.
Terry

The dynamometer tests can be found at www.modelaparts.net, the site for Pirianios Antique Automotive

[Terry, NJ]

That's the one! Thanks for posting! I liked it because of all the combinations that were used.
Terry

Originally Posted by Sparky

The dynamometer tests can be found at www.modelaparts.net, the site for Pirianios Antique Automotive

[Marshall V. Daut]

Don't let the canted angle of the "B" carb's flange and attendant bolt holes stop you from buying a "B" carb! The deflected angle can be sufficiently countered by grinding the shanks of the two 5/16" carb-to-manifold mounting bolts in the area of the lengths that passes through the manifold flange. This is not a high stress area, so grinding or using a lathe to thin down the bolt shanks in this area will not affect strength. The carb will not drop off. Make sure the bolts are long enough to grind away this portion. No need to grind much, if any, of the threaded portion of the bolts. After the upper shanks have been appropriately ground or turned thinner, some "wiggle room" will have been created to rotate the carb on a horizontal plane, thus closely approximating the Model "A" angle on the manifold. It won't be exactly the same angle, but much closer than had the bolts not been modified. You will easily be able to attach the choke rod now and have it function properly without undue binding. I have done this several times and it works quite well.
And yes - boring out the "A" intake central runner is the only way to really feel the advantage offered by a Model "B" carb. That extra air flow and power JET do help the Model "A" engine under power demands, sudden acceleration and higher speeds. Without boring out the "A" manifold or adding an expensive and odd-looking Model "B" manifold (the outer side of the center runner is FLAT across its face!), you will not really notice much improvement if you simply swap carbs. Life ain't that easy.
Marshall

[H. L. Chauvin]

FWIW:

After all B carburetor preparation is accomplished on an A engine, sometimes possibly overlooked as being insignificant is:

Maybe not realizing that on a four (4) cylinder, "up-draft" Model A carburetor, providing a 1-1/8" opening in the 1" restricted "A" gasket between the carburetor and the manifold is most important to avoid turbulence and cavitation.

Dynamometer tests have proven that any manifold and port opening rough surface or minor restrictions, which obstruct fighting gravity with an up-flow, "up-draft" Model A carburetor is not helpful for performance.

Unlike modern "down-draft" carburetors, with fuel mixture flow assisted by gravity, Model A fuel mixture flow "velocity" is most important in getting the already fully atomized fuel mixture to climb the long distance all of the way up to the Model A combustion chamber.

[john charlton]

Hi Terry

We will get storm "Jonas" the one that brought all the snow to NE USA .We will not get snow but very heavy rain instead so yet more flooding expected . "Jonas" is arriving early Weds ,luckily I live on high ground !!!.

John in unsettled low pressure weather on the way Suffolk County England .

[Marshall V. Daut]

Another thing to consider by guys, who have been dissatisfied with the conversion to a Model "B" carburetor, is the linkage adjustment. If a person simply swaps carbs and doesn't check whether the throttle opens fully afterwards, he will not be happy with the Model "B" carb. Because of the angle of the Model "B" carb on a Model "A" manifold - or even swapping manifolds and carbs - the accelerator arm on the linkage may need to be bent to ensure the butterfly valve on the carb opens fully. Too often the butterfly arm is bent or the distance is changed between the linkage arm ball and the ball on the butterfly shaft. I have seen swaps where the foot pedal is down all the way to the floorboard, yet the throttle on the carb is open only 3/4 of the way. The linkage MUST be checked any time there is a carburetor change.
How? Don't rely on simply pulling the carb's throttle open with your hand. That won't tell you anything. Have someone sit in the driver's seat and hold the throttle to the floor while you inspect the position of the butterfly throttle arm. It MUST bottom out against the stop peg, or else you're not getting full throttle. If adjustment is necessary, disconnect the throttle rod between the carb and the accelerator linkage arm, and with a vise grip, bend the linkage arm (NOT the carb arm!) forward. Then re-connect the throttle rod and check again. It may take a couple bends to achieve full throttle - but it's worth the effort to get full throttle travel.
I wonder how many guys were dissatisfied with their Model "B" carb swap without realizing the problem was simply that the carb was only getting 3/4 throttle?
Marshall

[DougVieyra]

Talking about a 'can of worms', who would have thought that a simple little carburetor switch could bring such a host of possible problems. The list of 'possibles', probables, maybe's, seems to grow with every consideration.

Luckily, mankind seems to have adjusted comfortably with 'close enough for government work'.

[Sparky]

Originally Posted by Marshall V. Daut

...And yes - boring out the "A" intake central runner is the only way to really feel the advantage offered by a Model "B" carb. That extra air flow and power JET do help the Model "A" engine under power demands, sudden acceleration and higher speeds. Without boring out the "A" manifold or adding an expensive and odd-looking Model "B" manifold (the outer side of the center runner is FLAT across its face!), you will not really notice much improvement if you simply swap carbs. Life ain't that easy.
Marshall

Well, it's not the only way

[Sparky]

Originally Posted by forever4

Is that the correct mahogany wood grain for fine point judging?

Absolutely!

[john charlton]

Hi Vince

Yes all 1932 to 1936 English "One Ton" AA trucks had the indented cowl . The steering column brace is a mirror image of the LHD and has an " AF" part number . They were fitted with the English made "B" carburetor these have "FORD" cast on the float bowl . They had the side bowl filter .As the the B carb was too tall it fouled the RHD steering column so the factory took a 45 degree slice out of the bottom of the inlet end to give clearance Only the first 6 of the one ton trucks had steel cabs the rest had Ford made wood cabs using the "mail truck " cowl . Although not pictured the 30 CWT truck used the "BB" cab on the "AA" frame .special steel filler pieces were used to allow this fitting . They used "A" front fenders ,splash shields and running boards . I had such a truck years ago but was too far gone to be restored so I broke it for spares . It was serialled as "AA" in the 4,900,000 range . They had the fully floating rear axle similar but not the same as the USA axle a lot of the part numbers are "AAE" prefixed . ( "E" meaning English )They were built to fit the "AA" frame . I do have a copy of the English "AAE" rear axle parts list . In England we have the "short ton " which is 2000 lbs and the "long ton" which is 2240 lbs . 1 CWT is 112 lbs this came from the days of coal selling to avoid short measure rather like a "bakers dozen "

John in wind and rain soon from "Jonas" Suffolk County England .

[Gabalus]

Originally Posted by john charlton

The "One Ton " AA truck was built at the Dagenham England plant into 1936 . These trucks were fitted with the Dagenham built model B engine and carburetor. Initially they were fitted with the RHD model A inlet manifold as it has the "peg" on which the manual advance/retard pivot is situated . These inlet manifolds were stock and not bored out so the 1/16" lip existed from the factory . In practise the setup worked just fine .I have this combination in my 1930 cabriolet . The extra gas flow given by boring out the manifold to suit the B carburetor only holds good at full throttle with your foot hard down . In normal driving the partially open throttle plate obstrucks the flow far more than the bore mismatch . My theory is the "lip" causes more turbulence and better gas atomisation so better combustion . Ford was happy with this setup but the later trucks were fitted with the "B" automatic advance/retard so the "A" inlet manifold was deleted .

John in we will soon get the bad weather from NE USA in Suffolk County England .

Few years ago, I saw a stock truck called AA4 with long wheel base, larger cab and lowered bottom doors(3passengers?), 1932 firewall hood shell. Do you speak about those trucks ?

Does anyone saw 1931 car with model B carb but with smaller ID ?

[Kevin in NJ]

How well built is your engine?

Do you have no problems running 60 MPH for extended (hours) periods of time?
Is it smooth with only the minor vibrations to be found on a 4 cyl engine?

My 30 fordor came with a B carb on an engine rebuilt in 1955. It had a bit of vibration. Ran 55 all day long and liked to get up and go. I switched it to an A carb with original jets. Ran the same.

I can see the B carb with enlarge manifold having an advantage on a well balanced properly rebuilt engine. Outside of that you really have other issues masking any advantage you might find in the B carb.