Ok, although it's bad form to respond to your own post, that never stopped
me before... Had some time today, so checked a few things out.
First off, I noted that during the 'stumble', the tach did not drop, but
tracked engine speed consistantly. I was unable to locate my timing light,
have to talk to my brother about THAT...
Since it only takes about five minutes, I bolted on my Weber DGV & it's
Pierce manifold, and fired it up. No 'stumble' problem whatsoever, just the
lame performance I always get with that carb.
Then I took the same SU's that I just removed, and bolted them onto my '80
MGB. Car starts & runs, but has the exact same 'stumble problem'.
Interesting, but probably have a vacuum leak on the 80 cause I could not get
the idle to slow down to below about 1200 - 1500 rpm.
So, could this problem be related to incorrect float height? Or perhaps just
carbs still set way to lean? Both?
Thanks for any insight...
--
-----------------------------------------------------------
Marc Siegel, Charm Net LLC eMail: smarc@abs.net
Baltimore, MD http://www.abs.net voice: 410/361-8160
> -----Original Message-----
> From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On
> Behalf Of Marc Siegel
> Sent: Friday, January 24, 2003 10:25 AM
> To: mgs@autox.team.net
> Subject: RE: SU rebuild ok, need a little advice
>
>
> Well, with the 20w50 in the dashpot, it was extremely stiff. What is an
> appropriate weight of oil for temperatures between 11F - 20F?
>
> >
> > Sounds weak, and putting lighter oil in the dashpot could well make it
> > worse. Workshop Manual says 40 thou from the chamber face to the lowest
> > part of the curve on the float. Mixture setting can be tricky,
>
> Can I infer that you think the mixture is too weak?
>
> My info on float height from the video was between 40 - 60 thou, and they
> used 50 thou to split the difference. The HIF floats seem to be a little
> more difficult to adjust in that it's not extremely clear where exactly on
> the float to measure the clearance from.
>
> > turning each
> > for maximum idle, then readjusting the other etc is an approximate way.
> > Lifting pin is another but can be even more tricky to judge, raising by
> > 1/16" should cause the revs to momentarily rise then settle
> back. If they
> > stay up it is too rich, if they die without rising too weak.
> Better when
>
> I was able to 'dial in' the correct setting when using the lifting pin
> method. This is with a warmed up engine, hadn't really tried when it was
> cold, since the video instructed me to let the engine come up to
> temperature.
>
> > warm? Choke functioning? Checked fuel delivery at the carbs?
>
> Choke IS functioning. There is fuel, but I will check the delivery rate,
> although I don't believe that to be a problem.
>
> > Should be at
> > least 1 pint per minute. On the principle that 90% of carb problems are
> > caused by the ignition did you fully set this up to? Is the
> tach dropping
> > with the stumble? Have you put a timing light on each plug lead
> > and checked
> > it is is still flashing during the stumble?
>
> No, but that seems like an easy way to determine that. I'll try it. Will
> recheck the timing while I have the light out. However, the
> vaccuum advance
> diaphram on my 25D is shot, and it runs on mechanical advance only. Been
> like that a long time. The vaccuum port on the manifold is
> plugged, there is
> no leak.
>
> I hadn't observed the tach during the occurance but will look next time I
> have a chance to mess with the car. I'm guessing that if the tach
> drops it's
> ignition related?
>
> Thanks for the tips!
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