I can confirm by experience that if one carb is running improperly, the
car will run badly - and may not run at all. I had this happen on a drive
back from the colorado conclave last year. I had problems on the drive
from the show through the Eisenhower tunnel - at which point I just
couldn't continue to move at any speed over 5 mph (well, except by
coasting, which I did to the bottom of the mountain). I spent about 8
hours trying to diagnose the problem, thought it was a carb, but couldn't
find it, and chased everything else (valves, ignition, etc.). Finally out
of desperation, I blocked one carb, and the car ran better (there is a
balance tube, you know). So, I disconnected the linkages connecting the
two carbs, and drove home on one carb - worked just fine. Didn't climb
hills quite as well, or accelerate as hard, but I could still outrun my
friend in his triumph (which was leaking oil badly -especially at high
rpm, and he wouldn't take it over 3000rpm), and it still would go freeway
speeds. Lesson learned - redundancy is good, redundancy is good - at
least on critical systems. This is one reason that batch fired injection
may be an advantage over sequential injection on modern cars.
This was on my MGA.
Phil Bates
'67 MGB
'58 MGA
> Hmmm, twin carbs so would still run (badly) if one were faulty.
Centrifugal
> advance issues in the distributor would affect starting as well as slow
> speed running. What is low during cranking and large throttle openings,
but
> maximum at idle and smaller throttle openings, is manifold vacuum as
used in
> your era of North American spec cars. Points plate ground wire broken or
> coil wire conductor broken inside the insulation? My first diagnostic in
> non-starting or running conditions is the (electric) tach, 2nd is the
timing
> light just to check for HT on the coil lead and each HT lead.
>
> ----- Original Message -----
> From: "Christian, Wellner L. CIV COMNAVAIRSYSCOMPATUXENTRIVERMD AIR
4.1.1.4"
> <wellner.christian@navy.mil>
> To: "MG Digest (E-mail)" <mgs@autox.team.net>
> Sent: Wednesday, January 21, 2004 1:30 PM
> Subject: Dead 1974 MGB - Quiz
>
>
> > Summary: In the above scenario, what would allow it to run perfectly
> above approx 4000 RPM and not run al all below approx 3500 RPM and be
> repeatable ??
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