Model B engine in an A

[36coupe]

I am rounding up pieces to build a 31 pick up. I have a model A engine that is seized and rusty from the head being left off & outside.
I might’ve found a Model A engines and an B engine locally that is not seized
I am not worried about being original as this is just random parts I’ve been finding.
Will the B engine fit the A transmission?
Is it a worthwhile upgrade? That is not too much work?
Thanks.

[Synchro909]

The Model B engines are more prone to cracking than the A engines so before you make any decisions, I suggest you have the B engine crack tested. If it is sound, it will be a decent upgrade. The Model A engine put out 40 hp, the B put out 50 so instantly, you have an extra 10 hp. There are B engines and there are B engines. The early ones had no counter weights on the crank shaft, the later ones did so if you can, opt for one of those. Both versions have a stronger bottom end to them - bigger journals and pressure lubrication to the main bearings.
As for the B engine fitting the A transmission, you will have to cut the bottom half on the flywheel housing off the sump (pan) and fit an A flywheel housing. Then, it will bolt right up.

[mcgarrett]

They say that there are two types of Model B engines; ones that are already cracked and those that soon will be!

[Bob Bidonde]

I have been running Model B engines in my Model A's for many many years. Never had a block crack, but I did have one throw a connecting rod threw the block. A stud securing the #4 Connecting Rod Cap failed. This failure could have been in a Model A engine, so it is not germane to the Model B engine.

The Model B engine is much more durable than the Model A engine because it has larger bearings and pressurized oil feed to mains. If you find a Model B in rebuildable condition, use it.
See this post https://www.fordbarn.com/forum/showthread.php?t=336697

[Joe K]

The Model B engine benefits from the stronger bottom end. But its challenged by a weaker upper end (cracks)

Most if not all of the horsepower difference between the two engines is in the "appurtences," specifically cam grind, carburetor, intake manifold. Other than these the two engines are similar.

My own experience with a Model B engine involves the Gordon-Smith air compressor conversion. Made for use with either A or B, the usual setup used the Model B engine which benefits by having "automatic" (centrifugal) advance with the Model B distributor - a benefit for an engine subject to load-no load operation (i.e. air compressor)

My particular Model B engine has a crack between the No. 2 exhaust port and the cylinder wall - a common location. It may have been chosen for this adaptation because the Gordon-Smith head has "filler pieces" designed to raise the cylinder compression by filling the space above the intake/exhaust valves, and the crack would normally be "covered" by the filler piece. I'm not sure of the "compression" of that gasket type filler.

Still, I have operated it in this condition for a fair amount of sandblasting but look to have the engine "lock & stitched" to cover/close the crack - and be sure.

Most information I have learned indicate this is VERY possible, but best done by someone with some experience.

Joe K

[Richard Knight]

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Having drilled through the deck surface of countless As and many Bs I can say I saw a trend. A blocks the decks all seem to be about 3/8"s thick. Early Bs the deck seems to be about 1/4" inch thick. Later Bs that have either version of the counter balanced crankshaft have the thicker decks. Installing hundreds of tapered pins was an education! As for the exhaust and intake ports that is a crap shoot. Some are very thick and some are very thin. Impossible to know until you try to repair. For anyone who has Jim brierlys book there are some interesting pictures of B ports along with a lot of other neat stuff.

[Synchro909]

As I have posted before, my firm belief is the reason for so many B blocks cracking is related tot he crappy distributors Ford used on them. After not so much use, they don't advance fully which means that the engine is running retarded. A retarded engine runs hot. Hot engines crack.
Simple as that!
If you were to ditch the original distributor and substitute an after market one with auto advance, you will be fine with a B engine.

[mcgarrett]

Originally Posted by Synchro909

As I have posted before, my firm belief is the reason for so many B blocks cracking is related tot he crappy distributors Ford used on them. After not so much use, they don't advance fully which means that the engine is running retarded. A retarded engine runs hot. Hot engines crack.
Simple as that!
If you were to ditch the original distributor and substitute an after market one with auto advance, you will be fine with a B engine.

Synchro,
You have presented an interesting argument worthy of further investigation. What distributor would you recommend? My brother just purchased 2 Model B engines hoping for a good one to install in his '33 Model B half ton pickup. We've already pulled one cracked engine with overheating problems - we'd sure like to avoid going thru this drill again!

[Synchro909]

Originally Posted by mcgarrett

Synchro,
You have presented an interesting argument worthy of further investigation. What distributor would you recommend? My brother just purchased 2 Model B engines hoping for a good one to install in his '33 Model B half ton pickup. We've already pulled one cracked engine with overheating problems - we'd sure like to avoid going thru this drill again!

I imagine the situation over there is pretty much like here. I went to an ignition specialist and asked them to make me a distributor to my specs. I'm sure FS will be able to put something together with the correct springs etc to give you the desired advance.

[nkaminar]

In the early 1970's I ran a B engine in an AA truck for a while. When I sold it the block was cracked.

[springerpete]

Another move might be finding an A diamond block to use. Understand they have improvements over the A.

[katy]

Originally Posted by Synchro909

As for the B engine fitting the A transmission, you will have to cut the bottom half on the flywheel housing off the sump (pan) and fit an A flywheel housing. Then, it will bolt right up.

Will a Model A oil pan and flywheel housing fit on a Model B block?

[Charlie Stephens]

Originally Posted by katy

Will a Model A oil pan and flywheel housing fit on a Model B block?

The Model A has a smaller rear main bearing which means you need to enlarge the pan for the larger bearing. The B rods will hit the sides of an A pan. You need to dimple the pan. I have heard that you could run low profile rad nuts and solve the problem. The flywheel housing fits.

Charlie Stephens