seando

1929 DeSoto Stewart-Warner vacuum fuel pump

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Yes the vacuum force is all about throttle position, the more you open the throttle the less vacuum you have, so there is a contradiction here in engine efficiency with these systems, the amount of fuel you have stored in the vac tank gets less and less the wider you open the throttle.

 

Giving it more gas to get up the hill will only make matters worse.

 

 

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On 9/03/2018 at 10:59 AM, old car fan said:

Did dodge and Desoto switch in 28 /29,my book somewhat shows it

If you mean when did they switch to mechanical pumps...

Dodge 1930: DC, DD, DE, DF first with AC fuel pump.

De Soto 1930: CF, CK.

 

If you mean switching brands of vacuum tank, Dodge 130, 131, 140, 141. 2252, DB, Domestic DA and some export used Kingston tanks. Models before these used Stewart Warner and some export DA had SW tanks. Some 130, 131 and 2252 also used SW tanks for foreign orders.

Edited by Spinneyhill (see edit history)

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Amazing info @Chris. Thanks. Have been out of town.

Sounds like it was designed to run uncapped? I can't seem to imagine how that works. I guess something changes as your going up the hill. 

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3 hours ago, seando said:

I can't seem to imagine how that works. I guess something changes as your going up the hill. 

 

 The fitting has an inbuilt venturi fed by the hole which you have blanked off. The venturi is designed to create an even bigger (atmospheric) pressure drop for the vacuum source at the top of the inner tank, which in turn will lessen the effect of manifold vacuum drop as you open the throttle; particularly helpful if you have a long uphill drag.

 

Of course this is really only beneficial when you have a inlet manifold source of vacuum, its therefore unnecessary with an oil pump vacuum source which increases vacuum with oil pump (engine) rpm.

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