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

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



forever4 said:
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.
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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 .
 
Charlie Stephens, post #4: "Is there any reason to bore an A intake instead of using a B intake?"
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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'.
 
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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]
 
Terry said:
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
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The dynamometer tests can be found at www.modelaparts.net, the site for Pirianios Antique Automotive
 
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
 
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.
 
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 .
 
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
 
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'.
 
Marshall V. Daut said:
...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
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Well, it's not the only way :D
 

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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 .
 
john charlton said:
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 .
Click to expand...

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 ?
 
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.
 
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