datsun-roadsters
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Re: SUs & smog

To: "L Jordan" <ay107@lafn.org>
Subject: Re: SUs & smog
From: "Fred Schroeder" <roadster@texoma.net>
Date: Fri, 16 Aug 2002 11:11:48 -0500
Possibly.  It consists of a small steel ball and a flat spring. Crude but
effective way to maintain pressure.  If the spring were to break or deform
in some way it would fail to maintain pressure. Or, if a piece of crud got
stuck between the ball and the seat.  The best way is to check you pressure
at idle.  It should read 3-4 lbs.

One thing to think about; many people confuse pressure with flow.  You might
have perfect static pressure but the flow is impeded.  This is especially
true of the Roadsters.  Due to the circulating fuel setup, the pressure will
be fine.  But, you have no flow into the carbs due to clogged filters.  I'm
referring to the screen filters inside the banjo fittings on the carbs.  The
main filter can cause a similar problem.  Good flow and pressure at idle/low
speeds but starves out as flow demand increases.

Best regards,

Fred Schroeder
Denison, TX
SRL311-13359
TDROC
Reg e-mail  sitsinwest@texoma.net
Home page  http://home.texoma.net/~sitsinwest
----- Original Message -----
From: "L Jordan" <ay107@lafn.org>
Cc: <datsun-roadsters@autox.team.net>
Sent: Thursday, August 15, 2002 10:31 AM
Subject: Re: SUs & smog


> Fred,
> Could this valve go bad ,thereby reducing fuel pressure and affecting
> performance via fuel starvation, much like a bad fuel pump, only on a
smaller
> scale?
> thanks,
> Linda
>
> Fred Schroeder wrote:
>
> > Sounds like you have the evap fuel setup. From what I've seen removing
it
> > would be a chore.  Plus it doesn't cause any problems.  I'd just leave
it
> > alone.
> >
> > The 'fuel return valve' is basically a simple pressure regulator.  The
> > Roadsters have a continuous flow fuel system.  Gas circulates constantly
> > allowing the carbs to take whatever they need.  This valve maintains a
> > pressure of around 3 lbs on the carbs and allows the rest to return to
the
> > tank.  This is one reason the Roadsters don't vapor lock.  I've driven
mine
> > in the Arizona desert in the dead of summer and never had a problem.
I've
> > heard claims of vapor lock but have never witnessed it personally.
> >
> > Best regards,
> >
> > Fred Schroeder
> > Denison, TX
> > SRL311-13359
> > TDROC
> > Reg e-mail  sitsinwest@texoma.net
> > Home page  http://home.texoma.net/~sitsinwest
> > ----- Original Message -----
> > From: "Brad Holmes" <bholmes@monk.aum.edu>
> > To: <datsun-roadsters@autox.team.net>
> > Sent: Friday, August 16, 2002 8:44 AM
> > Subject: SUs & smog
> >
> > > Since were on SUs, I recently bought a 70 - 2000 California car that
> > > has been de-smogged. The PO or the pre-PO has removed much of the
> > > devices and plugged ports and did a recurve. There are still a bunch
> > > of lines running around, to and from the tank. A couple questions.
> > > 1. Can ALL the rest of the smog equipment also be removed and lines
> > > and ports plugged, on the tank and in the engine room?
> > > 2. Can the vent on the dip stick be capped off?
> > > 3. What is/was the purpose of the "valve, fuel return assy, rear"
> > > next to the rear SU? (F8B-1, item 119, top left of the pic in the
> > > parts manual) http://www.gordon-glasgow.org/Images/8B.gif
> > > Can the valve be removed and a regular fitting be installed?
> > >
> > > Thanks
> > > Brad Holmes
> > > 68 - 2k, Solex
> > > 70 - 2k, SU
> > > SEROC
> > > OROC
> > >
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