My dear spouse gave me a Gunson's Colortune for Christmas, which I
put to immediate use on my '67 MGB. Part of my 12 step program to More
Power (with the least cash outlay), was to purchase an intake manifold
from Seven Enterprises, and a pair of ex-Volvo SU HS-6 carburettors
from a local (when I lived in Southern California) junk yard. I had
them rebushed, fitted blue springs, and after a bit of trial and
error, SY needles. I am using Moss genuine SU dashpot oil, and I also
have a centrifugal-only distributor. With my new Colortune, I set the
idle to just-barely-yellow on the #1 and #4 cylinders. Now my idle is
fairly smooth (about 850 RPM), acceleration is just fine, and
steady-state running is also just fine. However, when I drive to town at
an almost legal 60mph, then back off the throttle to make the 90
degree turn off the highway, strange things happen. First, when I blip the
throttle as I downshift, doing all that fancy heel-toe stuff (I have a large
size accelerator pedal from a later MGB), the engine kind of gags, then,
after I make the turn, I continue on over-run in second gear about one block
to the stop sign. If I just put in the clutch and shift into neutral
at the stop sign, the engine dies. If I try to blip the throttle, it acts like
a
normal carb with a bad accelerator pump. If I just floor the throttle and hold
it, the engine comes back to life.
Questions: The temperature is in the 40s F here during the day, high
20s at night, is my dashpot oil too thick, holding the pistons up for too
long? Would changing to that magic ATF stuff help? Should I try heavier
springs, and if so, what color?
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