Spitphiles,
I'm still trying to adjust my twin SU setup on my '71 without success, despite
following the instructions of Haynes, the VTR site, an MG site, and Bentley. The
car idles great with equal hiss at both intakes but begins to miss and die off
(no power) above idle along with occasional backfires, etc. Timing, points,
plugs, etc. have all been checked out.
Questions:
How many turns of the jet adjusting nut (up or down) are commonly needed with
properly set up SUs to reach a reasonable mixture setting from the initial
position (two full turns down from jet flush with the bridge)? I am screwing
mine out (richer) so many turns that I'm afraid the jet is going to fall off of
the bottom. However, this is the position where I begin to get the slight,
momentary engine speed increase described in the manuals when the piston is
lifted 0.8mm. Does this indicate that the jets and or carbs are badly worn, and
need rebuilding? The car still runs lousy at these settings.
Would the carbs need about the same degree of adjustment to reach the correct
mixture if they were in good condition? The back seems to need a lot more
enrichment than the front. Also, there seems to be some slop in the positioning
of the jet of the rear carb when it's level with the bridge.
What adaptor is needed with a Colortune to work in a Spit engine? Does a
Colortune come with the right on, or does it need to be ordered? Is this the
magic tool I need to make this car run properly again?
Sorry for the long and wordy post, but this car has been off the road since
early May with this problem, and I'm slowly losing my mind. It all started when
I bought new air filters!!
Regards,
Bob Waid
71 Mark IV FK4081L
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