Hello Friends,
I have a difficult problem and would like to hear
your thoughts... well, the constructive ones anyway.
SET-UP: My '76 Midget 1500 has a Weber 32-36 DGV
carb installed on the usual conversion kit manifold;
That is, the manifold where the little plenum sits
lower than the inlet ports. The runners tilt slightly
upward toward the head. The base of the DGV is a
round-cornered rectangle sitting over a similarly
shaped plenum. The plenum size is about 2" x 4" and
1.5" deep to the plenum floor. By design, the outer
choke of the carb sits preferentially over the plenum
where the #1 and #4 runners are fed. The inner choke
sits over the #2 and #3 feed points. Of course, the
DGV is a progressive carb so the secondary (outer)
choke does nothing until about 2/3 throttle setting.
The plenum does the mixing. So there you have the
set-up.
OH YEA: The ignition is new and the problem is the
same as before the old Pertronix Ignitor failed.
PROBLEM: Cylinders #2 and #3 see a perfect mixture, or
at least a plug cut shows a nicely light brown color
on the central insulator. Cylinders #1 and #4 are
heavily coated in dry carbon and the exhaust is laden
with black smoke. #1 and #4 are running WAY too rich
while #2 and #3 are perfect. Interesting challenge
with a plenum-based manifold! The problem is to
understand WHY this hapopens and then to fix it.
SOLUTIONS:
(1) Can the outer choke be flooding liquid gasoline
past the throttle plate, dribbling down into the
plenum and being preferentially sucked into #1 and #4
causing a grossly over-rich mixture while leaving the
vapor-phase charge right for #2 and #3?
(2) Can this problem be caused (in any way?) by bad
valve adjustment? The valves are not noisy so they
are not too loose but a compression check also says
that they are sealing properly and therefore, probably
not overly tight.
(3) Can flying monkeys from outer space be tweaking
the mixture to just screw with my head? I know that
this is unlikely but I don't want to discount any
possible scenario at this time.
Thoughts please?
rick
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