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Old 05-11-2013, 05:12 AM   #1
johnbuckley
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Default fuel pressure to Model B carb?

What should be the fuel pressure to a Model B carb if using a fuel pump (mechanical or electric). ( and please don't just say "enough but not too much!!")
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Old 05-11-2013, 06:13 AM   #2
James Rogers
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Default Re: fuel pressure to Model B carb?

1-2#
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Old 05-11-2013, 06:21 AM   #3
johnbuckley
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Default Re: fuel pressure to Model B carb?

I believe a full Ford A gravity tank gives just slightly under 1 psi . So if one is using a B carb on an A with standard gravity feed tank should one add a pump to raise the pressure a bit?

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Old 05-11-2013, 06:56 AM   #4
Phred
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Default Re: fuel pressure to Model B carb?

Pump probably not necessary.
Anecdotally, I ran a B carb on my '30 Murray for years without a problem.
Hope this helps.
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Old 05-11-2013, 07:00 AM   #5
ken ct
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Default Re: fuel pressure to Model B carb?

Most will need a pump w/ 1 1/2 to 2 1/2 # about like a V8. Pumps are almost identiticle to a V8 pump. ken ct. OMO.
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Old 05-11-2013, 07:28 AM   #6
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Default Re: fuel pressure to Model B carb?

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Generally speaking, you only need a pump when you use a downdraft carb. Even then you can use a 12 volt pump on a 6 volt system and it will work perfectly without a regulator.
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Old 05-11-2013, 03:28 PM   #7
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Default Re: fuel pressure to Model B carb?

I do not run a pump on my B carb which is in the stock position, just completed some 1500 miles of which some were very steep up & down, 120 kph on open highway, never needed a pump. However if you wish to run one 2psi would be plenty.
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Old 05-11-2013, 04:40 PM   #8
Purdy Swoft
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Default Re: fuel pressure to Model B carb?

I run dual B carbs on two of my cars with no pump and they perform well. I don't use the float spring on my B carbs.
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Old 05-11-2013, 04:57 PM   #9
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Default Re: fuel pressure to Model B carb?

Anyone running dual 81's on a B with a stock B fuel pump successfully?
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Old 05-13-2013, 06:48 PM   #10
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Default Re: fuel pressure to Model B carb?

No pump required and no float spring either.
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Old 06-12-2013, 08:59 AM   #11
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Default Re: fuel pressure to Model B carb?

I was curious if its worth switch to a Model B carb on my A engine. Is there much performance improvement?
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Old 06-12-2013, 10:05 AM   #12
Purdy Swoft
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Default Re: fuel pressure to Model B carb?

If everything is right and the intake runner is opened up to model B size you will gain a little top end. You won't feel the difference in the seat of your pants. If the engine has some mods like higher compression, better cam,port work, hotter ignition and free flowing exhaust, Two B carbs on a larger intake manifold will make more of a noticable improvement. When the high speed jets kick in on my speedster with dual B carbs, I can really feel the power

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Old 06-12-2013, 10:51 AM   #13
ken ct
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Default Re: fuel pressure to Model B carb?

You guys have to remember 1 or 2 updrafts sit much lower on the engine and gas tank than 1 or 2 downdrafts which are up much higher. ken ct.
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Old 06-12-2013, 12:59 PM   #14
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Default Re: fuel pressure to Model B carb?

With my Weber downdraft, I still have about a 6" fall, which seems to be sufficient, even with a near empty tank. It was still running when I was able to put 10.695 gallons in the tank.
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Old 06-12-2013, 09:51 PM   #15
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Default Re: fuel pressure to Model B carb?

To pump fuel from the rear tank to the front tank, I used a regulator set at 2lbs on o zenith or tillotson.... I don't remember. We all had additional tanks on the World Tour.
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Old 06-13-2013, 12:43 AM   #16
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Default Re: fuel pressure to Model B carb?

Skryla, I just got my '31 on the road and it is running a diamond block B motor with dual 81's. I'm running the stock B fuel pump and have had no problems with fuel delivery.
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