[DeTomaso] Stumbeling.

Doug Braun doug at silicondesigns.com
Thu Jul 16 18:43:35 EDT 2009


Unfortunately, I've never taken apart a Demon carb, only Holleys.  Others on
the forum know a lot about Demons so hopefully you'll get an answer from
them.  It likely has a power valve like the one in a Holley, or it may even
use a Holley power valve but I don't know.  If it does have one like a
Holley, it should be stamped with a number on it that will tell you at what
vacuum level it operates.  Above that vacuum level it's closed and below
that level it's open and richens the mixture.  If it is blown, it will
richen the mixture all the time which may be your problem.  The most common
valve is a # 65 which means it operates at 6.5 inches of vacuum.  I'd start
by replacing the valve with one identical to what's already in there and see
if it cures your problem.  If you have a very radical camshaft that prevents
your engine from creating high vacuum values, you could also try a # 45
valve to see if it cures your problem.

Doug Braun

-----Original Message-----
From: gudmund frøland [mailto:gudmundfroiland at yahoo.no]
Sent: Thursday, July 16, 2009 1:51 PM
To: Doug Braun
Subject: RE: [DeTomaso] Stumbeling.



It is a Demon dubblepumper, i never know how it worked from beginning.It`s
been on the car sence i bought it. The car came from US when i bought it.It
works fine if start from 0 with full troottle , onley when cruse and give
full it stuble?
Best regards     Gudmund Froiland   


--- Den tor 2009-07-16 skrev Doug Braun <doug at silicondesigns.com>:

> Fra: Doug Braun <doug at silicondesigns.com>
> Emne: RE: [DeTomaso] Stumbeling.
> Til: "gudmund frøland" <gudmundfroiland at yahoo.no>
> Dato: Torsdag 16. juli 2009 19.29
> I assume this is a Holley carburetor,
> correct?
>
> If so, had this carburetor been running properly on the car
> and then
> recently stopped working properly or was it recently
> installed and has never
> worked properly?
>
> Doug
>
> -----Original Message-----
> From: gudmund frøland [mailto:gudmundfroiland at yahoo.no]
> Sent: Thursday, July 16, 2009 10:14 AM
> To: Doug Braun
> Subject: RE: [DeTomaso] Stumbeling.
>
>
>
> How can i determen what size powervalve i would need? I
> understand there are
> different sizes.
> Best regards     Gudmund Froiland   
>
>
> --- Den tor 2009-07-16 skrev Doug Braun <doug at silicondesigns.com>:
>
> > Fra: Doug Braun <doug at silicondesigns.com>
> > Emne: RE: [DeTomaso] Stumbeling.
> > Til: "gudmund frøland" <gudmundfroiland at yahoo.no>
> > Kopi: "DeTomaso Forum" <detomaso at realbig.com>
> > Dato: Torsdag 16. juli 2009 17.31
> > You could have a bad power valve and
> > they are so inexpensive you should just
> > replace it.  What may be happening is that your
> blown
> > power valve is
> > constantly providing far too rich of a mixture between
> off
> > idle and
> > upper-mid RPMs.  It's not until you get enough RPM
> up
> > to bring enough air
> > through the carb to handle the extra fuel from the
> power
> > valve that it
> > clears out.  If you're blowing black smoke while the
> > engine is stumbling
> > that's a good clue your power valve is gone.  Or
> > better yet, have someone
> > follow you when it happens and have them tell you if
> the
> > exhaust smells rich
> > when it happens.  Or just replace the valve which
> may
> > be the quickest thing
> > to do.  Be sure to buy new bowl and metering block
> > gaskets before you
> > disassemble the carb.
> >
> > Hope this helps
> >
> > Doug
> >
> > -----Original Message-----
> > From: gudmund frøland [mailto:gudmundfroiland at yahoo.no]
> > Sent: Thursday, July 16, 2009 1:43 AM
> > To: Doug Braun
> > Subject: RE: [DeTomaso] Stumbeling.
> >
> >
> >
> > Thanks. Acc pump are working ok. No play on the
> cam.Its not
> > just stumbling
> > for a second and comming,it works like when i give
> full
> > trottle it stuble al
> > the time until i eaze on trottle, then i can go for
> it
> > again more gently and
> > it pulls ok.I was wondering how that power valve are
> > working ?
> > Best regards     Gudmund Froiland   
> >
> >
> > --- Den tor 2009-07-16 skrev Doug Braun <doug at silicondesigns.com>:
> >
> > > Fra: Doug Braun <doug at silicondesigns.com>
> > > Emne: RE: [DeTomaso] Stumbeling.
> > > Til: "gudmund frøland" <gudmundfroiland at yahoo.no>
> > > Dato: Torsdag 16. juli 2009 00.07
> > > Check that the accelerator pump is
> > > working.
> > >
> > > Doug Braun
> > > blue 73L #5505
> > >
> > > -----Original Message-----
> > > From: detomaso-bounces at realbig.com
> > > [mailto:detomaso-bounces at realbig.com]On
> > > Behalf Of gudmund frøland
> > > Sent: Wednesday, July 15, 2009 2:50 PM
> > > To: Detomaso at Realbig. Com
> > > Subject: [DeTomaso] Stumbeling.
> > >
> > > I have been out crusing a little and if i
> accelerate
> > with
> > > full trottle it
> > > pulls good but if i cruse and give full trottle
> my
> > engine
> > > just stumble and
> > > wont pull any before i lighten the trottle.When
> it
> > start
> > > pullin i can go for
> > > it and it pull strong. Are there any good advise
> here.
> > No
> > > pinging so i
> > > belive the timing is right.
> > > Pantera 06872    Gudmund Froiland
> > >
> > >
> > >
> >
> >
> >      
> >
> _________________________________________________________
> > Alt i ett. Få Yahoo! Mail med adressekartotek,
> kalender
> > og
> > notisblokk. http://no.mail.yahoo.com
> >
> >
> >
>
>
>      
> _________________________________________________________
> Alt i ett. Få Yahoo! Mail med adressekartotek, kalender
> og
> notisblokk. http://no.mail.yahoo.com
>
>
>


      _________________________________________________________
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