Duplex Carb on a Model B

jgc · Feb 12, 2013

Can a Model B be modified to use a duplex carb, as used on later generation JD tractors?

If yes,,,, what is involved; carb, linkages, manifold, head, other components that need to be moved or modified, etc, etc???

Regards,
JGC

John T · Feb 12, 2013

Not that Im aware of....Its the MANIFOLD thats important, I think the duplex carbs and duplex mainfolds have seperate chambers for each cylinder while the old single barrell manifolds dont. Thats why at slow idle (on single carbs and manifolds) if you pull one plug wire it almost dies while if you pull the other one it dont seem to make much difference NOT SO on duplex carbs with a seperate carb barrell and manifold chamber for each clinder.......

Am I correct????

John T

Mike M · Feb 12, 2013

Only thing gained is a better idle. Not really any HP differance between a model B and a 50

2-banger · Feb 12, 2013

you need a 50 hd..manifold and carb..50 hd feeds each cyl seperate where the orginal b hd only has 1 intake port both cyls draw from it.it will make a little more power and be easy to tune

gtx1967jewison · Feb 12, 2013

Imo a single carb is easier to tune. Especially a dltx v.s. a duplex. All my singles idle nicer & slower than most duplex tractors at the shows. Half as much to go wrong & if it plugs you can actually access the ports to clear them.

jd b puller · Feb 12, 2013

Agree with most of the comments. Not sure how it would be easier to tune as all the duplex carbs I've seen have fixed load jets with that single screw at the bottom that has very little impact on mixture. My experience with taking a 2 barrel carb, and modifying the manifold to adapt it to a single barrel Head was that it worked ok at wide open but will lose all bottom end unless the motor is really big.
The 50 head has 10 head studs, the B has 9 and not in the same location. You can put a 50 block into a B with a little work.

What goals are you trying to accomplish?

Mike M · Feb 13, 2013

I would imagine that most of those with the duplex carbs. have not been adjusted correctly.
Like you said they are harder to tune. You need to short out each cyl. and adjust each cyl.to idle at the same RPM.

jd b puller · Feb 14, 2013

Agree with most of the comments. Not sure how it would be easier to tune as all the duplex carbs I've seen have fixed load jets with that single screw at the bottom that has very little impact on mixture. My experience with taking a 2 barrel carb, and modifying the manifold to adapt it to a single barrel Head was that it worked ok at wide open but will lose all bottom end unless the motor is really big.
The 50 head has 10 head studs, the B has 9 and not in the same location. You can put a 50 block into a B with a little work.

What goals are you trying to accomplish?

buickanddeere · Feb 15, 2013

Cheaper and run better, have live hydraulics plus the option of live pto and optional PS if you just trade the B for a 50 or 520.

Duplex Carb on a Model B

jgc

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John T

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Mike M

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2-banger

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gtx1967jewison

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jd b puller

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Mike M

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jd b puller

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buickanddeere

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