Boring a 125ci AF motor to a 200ci A motor

[montanafordman]

Originally Posted by johnbuckley

Great Britain offered the smaller bore size because of the road tax system in place there at the time. (though the 3285cc engine in cars was also available as an option). The smaller diameter bore brought the fiscal horsepower rating of the car in at 14.9hp, the larger diameter gave a fiscal hp rating of 24hp and attracted a higher annual tax paayment. This tax system was meant to favour the UK vehicle home manufacturing industry ( think small engined Austins and Morris). But in fact it shot the Uk industry in the foot as their cars became less and less suitable to export. The larger bore Model A engine was used on commercial vehicles in the UK which had different tax regime.
The smaller diameter bore engines of the Model A were GB specific though a few obviously made it across to europe and the empire countries.

Ok, That makes sense. Thanks! Now I understand why we drew a line in the sand with taxes on stamped paper and tea... I kid... I kid...

Does anyone know how the engine weight was affected by the smaller displacement? Practically speaking how much of a performance detriment was this really in top speed and hill climbing ability?

[Juggler]

Weren't the 14.9 engines available from new in France and Japan? Presumably for similar road tax/hp tax (read protectionist) reasons?

[johnbuckley]

Originally Posted by Juggler

Weren't the 14.9 engines available from new in France and Japan? Presumably for similar road tax/hp tax (read protectionist) reasons?

Didn't know that. The knowledge you amass from this website is amazing.

[johnbuckley]

Now I understand why we drew a line in the sand with taxes on stamped paper and tea... I kid... I kid...
IS THAT TEA BREWED YET?
Don't know the weight difference- I would guess not much.
Cruising speed is not much different, it's really on the hills that the cubes tell. Many over here have now been swapped for the 3.3 engine

[d.j. moordigian]

Doing a quick calculation with a "stock" stroke the bore is right at 3.060".

[johnbuckley]

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According to one of "our" manuals : bore 3.0552 ,capacity 2043cc=124.6ci. stroke same at 4.25". ring gaps corresponding slightly tighter. Other differences with the 2043cc engine were in the smaller jets and venturi size, and a slightly smaller bore of inlet manifold. As far as I know there were no changes to valvesor cam shaft. To compensate for the lack of grunt the back axle was 4.55:1 . Also the cylinder head was different to give a smaller volume. Have no performance specs, but when in convoy the 2043cc cars keep up OK until it comes to hills . Limeys rarely souped them up at that time; they has Austin 7s to play with. All this research has got me scabbling through old books - Rowdy- I'm wondering if the authorities I've beeen consulting are wrong and that some 3.3 litre engines destined for RHD vehicles were in fact designated AF after all!!

[quickchange]

I have two B small bore engines here in NZ , Although big end journal the same as big bore the rods are narrower at piston end, Head studs & valves are in a differant location along with the spark plugs, ONLY the crank is the same as big bore , Probally as much power as an austin 7 ???

[Tudortomnz]

The Model A ''small bores'' were specific to countries that had horse power taxes on private vehicles. This was mainly Britain, France & some other European countries.
Australia , New Zealand & Sth Africa had no added tax on engine size, so no small bores. But, from 1932 Ford UK started to sell vehicles here as they were lobbying for preferential market access in British Dominions ; the small bore B4 became available in small numbers.
Little known was that Ford Canada offered the small bore option & they were sold in Singapore in the Model A era which may have had HP tax. It is likely they used the English produced engine as there was a production connection between Ford Canada & Ford Britain.

AF stamped blocks are not small bore specific. These are known on some Model A sold in Sth America which are US produced RHD cars with the standard size engine.
AF can be any part of a Model A vehicle sold outside the US.

[Hotrodfil]

Here's inside a BF for reference - you can see the small bores.

[Hotrodfil]

That's not a small bore AF casting that's for sure.

[Tudortomnz]

I think that engine block [ Rowdys photos] is from a Sth American car.
Canada did not use those letters, so not from DownUnder.

[Rowdy]

As I said before it was likely made in South Africa. At some point it made its way to Australia, then to the US. The car was restored by a local guy and the engine was replaced with one that did not need a full rebuild. The person that restored it moved to Iowa sometime in the late 80's and passed away in the mid 90's. The cars current whereabouts are unknown from there. Rod

[johnbuckley]

Agree with you absolutely Hotrodfil..That's not a small bore AF casting that's for sure. ..(#29).. now look at the Juggler's excellent photo (#10) for a small bore engine casting and note the land between 1 and 2, and 3 and 4. and compare it it a std bore casting which only has land between 2 and 3. Check out the number www.fordgarage.com and maybe consensus would agree it's a Rouge std bore for a RHD ( and thus likely export to a RHD country other than British Empire- one in South America perhaps?) PS did you have any RHD As in the home market USA? Sorted?