Model A carb on a model B engine?

[johnbuckley]

A friend has a B engine, spares for the B carb are difficult to source over here. Can the B engine be run reasonably well with an A carb? Should the jet sizes be increased for this scenario?

[quickchange]

John what do you need re B carb , have spares here .

[johnbuckley]

Thanks, he needed an idle jet - eventually sourced one here but would like an A carb as a spare ( if it works on a B). He may contact you anyway re further B carb spares.

[Chippy Minton]

My car has a B block but an A head, carb and distributor. It runs beautifully.

[Synchro909]

The B motor is not much different from an A motor. They are basically the same motor. Same bore, same stroke, a little more compression, slightly different cam timing and not much else. I haven't tried it but I can't see why an A carburetor wouldn't work just as well on the B engine as on an A.

[hewe]

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The only difference is the intake throat size allows more air /fuel in.

[RandyinUtah]

This is only true if you use a b type intake manifold.

[Synchro909]

I can't see the size of the manifold making any difference. The carby is still feeding the same sized engine running at the same revs.

[tiger.1000]

John,

I may have a complete spare B carburettor, ultrasonically cleaned and ready to fit.
£150.00 if interested.

[Terry, NJ]

LB 150? OMG! The most I've ever paid is about $20. To be honest, I've seen a lot for sale for more. Usually for about $75 -$90 for a good working unit. One thing to watch for is a broken mounting ear/tab. They break very easily. However, if you are good with a milling machine, you can make a new steel base and braze it to the top of the carb. It's just a plate with two 5/16 x 18 threaded holes and a 1 1/4" (30 mm?) center hole. The "A" manifold should be drilled out. The main runner should be around 1.300. If you use a 30mm drill or a 1 1/4 drill and polish the inside surface, it should be close. Any bigger and the metal is getting too thin. With a "B" carb, this modification has been documented to give you about three HP. With a stock "A" carb, there is some improvement too.
Terry

[Richard Lorenz]

I might be wrong, but I believe that the flange that holds the carburetor on a B intake manifold is slightly rotated from what an A manifold has. You might need to use a 1/4-inch bolt and nut (instead of the standard 5/16) in one flange hole in order for the A carburetor to be lined up straight with the choke control rod.

[johnbuckley]

Originally Posted by tiger.1000

John,

I may have a complete spare B carburettor, ultrasonically cleaned and ready to fit.
£150.00 if interested.

. Thank you , personal message sent.

[RandyinUtah]

Terry is very correct in stating that an A intake manifold main runner drilled out to 1 1/4 inch will match very close to the size of intake manifold of original Model B. I make this modification even if I'm going to run a stock model a zenith carb.

[Bob Bidonde]

Model A Zenith and Model A manifolds on a Model B engine with a 5.5:1 Model A type cylinder head. This combinations runs excellently, especially on the highway.