Model A and Model B Engine Difference?

[spdway1]

Sorry for the dumb question:
What is the difference between the Model A and Model B engine?

Pros and cons?

Thank You.
Don Jr

[Dick Carne]

B Model engines (sometimes referred to as B and/or C Model engines, depending on whether the crank had counter balanced weights) have heavier cranks and rods, and I believe were rated at perhaps 50hp as opposed to the Model A's 40 hp. Some of this could be attributed to the higher compression head. Intake manifolds were slightly wider to allow better intake airflow. As far as appearances, the left side of the B engine appears almost identical to that of a Model A; however the right side is conspicuously missing the oil return line - also, the timing pin on the B has a slightly different placement than that of the A, so timing covers are not interchangeable. B Model oil pans are also different, but can be modified to accept a Model A flywheel housing by removing the rear-most portion of the pan that would otherwise mate to the B flywheel housing. I'm certain that there are those that are much more knowledgeable on this topic than I, and may wish to correct me on some of these items, but in general, these are my initial thoughts. Hope this helps.

[Synchro909]

I'd like to chime in here with a question about the B motor - not wanting to hijack the thread but what is the diameter of the B main bearing journals? I know they are larger than those in the A motor but by how much??

Another pretty obvious difference between the two in the three bolt water pump on the B motor vs four bolts on the A motor

[colin1928]

Pro B have a improver oiling system larger crankshaft journals and better breathing
Con thinner castings prone to cracks

[johnneilson]

Originally Posted by Synchro909

I'd like to chime in here with a question about the B motor - not wanting to hijack the thread but what is the diameter of the B main bearing journals? I know they are larger than those in the A motor but by how much??

Another pretty obvious difference between the two in the three bolt water pump on the B motor vs four bolts on the A motor

Mains are 2" (1.9985)
Throws are 1 7/8"
More material in the crank if you wish to drill for full oiling to the rods.
The Main bolts are spaced out further to allow for the larger crank also.

Oil pan and flywheel housing are different, much written on this subject.

For me the most important difference is the oiling system on the "B".

J

[Synchro909]

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Thanks, johnneilson That's what I wanted to know.

[Mike V. Florida]

This site will be of help;

http://www.fordgarage.com/

[John Stone]

I've always heard there are 2 types of B engines. Those that are cracked and those that are going to crack. A engines are a little better in that respect.

[katy]

B engines also have the fuel pump mounted on the RH side.

[Bob Bidonde]

The Improved 4 Cylinder Engine as Ford Motor Company called it, is much more durable than the Model A engine because it has:
>10 more horsepower;
>Larger diameter main bearings;
>Larger diameter connecting rod bearings;
>Pressure oil supply to the main bearings noticeable by a much larger valve chamber & cover, and the disappearance of the oil return tube;
>4.6:1 compression ratio cylinder head;
>Larger carburetor (higher CFM) for better breathing;
>Slightly improved camshaft grind for better breathing;
>Mechanical fuel pump because the gas tank went to the rear of the cars. The camshaft has an extra lobe to drive the fuel pump;
>Water pump with a larger diameter impeller and 3-bolt mounting;
>Distributor with centrifugal spark advance, an adjustment for the octane rating of gasoline and a smoother profile cam;
>Front timing gear cover with the timing pin moved 9.5 degrees advanced;
>As the engine evolved, a counterbalanced crankshaft was added and the flywheel was reduced in weight about 12 pounds;
>Champion C4 spark plugs;
>Crankcase oil pan has an integral sheet metal flywheel housing;
>Oil breather tube and cap are larger in diameter;
>All of the changes made to late 1931 Model A engines including lowered connecting rod dipper tray and shielded oil pump;
>Oil outlet opening in the oil pump casting went from round in the Model A to rectangular in the Improved Engine;
>Intake manifold with a larger internal diameter;
>A different exhaust manifold to accommodate the later body designs;
>Intake & exhaust valves made of improved materials.

[John Stone]

Actually the B came with 3X plugs. The V8 came with the C-4's.