Last night I had a little time after work and thought I'd try setting
the idle on my '64 MGB with my recently purchased Gunson Color Tune.
Things didn't go according to the instructions, so I could use some
advice.
Background is that the engine seems to be in good shape--even
compression of 155 psi in all cylinders, newish Mallory coil and
wires, Pertronix ignitor in the distributor, timing set to 14 deg
BTDC, NEW SU CARBS...
In setting the mixture by color, it took a LOT of leaning out from my
initial carb setting to get the flame color to go from yellow to
blue. With both carbs adjusted for bunson blue flame, idle was
rough, and out on the road the engine stumbled badly (too lean?)
Also, in looking at ignition, there seemed to be a lot of
uneveness--you could watch the flame color change / drift from blue
to yellow-blue.
My first thought is that I don't know anything about the cam, and
that maybe the problem is that it isn't stock, and has too much
overlap (exhaust gas contaminating the mixture, requiring richer
mixture?) But I am baffled. Anyone have experience with the
ColorTune? Is it a mistake to use it on a dual carb LBC? Is the
"lean drop" method superior if you don't have to pass smog tests? I
feel lucky that I don't have to smog it--as it sits it probably
wouldn't pass...
Chris Attias
'64 MGB
'84 Alfa Romeo GTV-6
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