Marcus (and Scott Fisher):
This may sound stupid, coming from a real novice SOL and not knowing
exactly which carbs Marcus has... I will assume SU HS2 since that's
the only one I know <g>.
After going back through the last 3 weeks of adventures with Marcus' car,
I am going to >assume< that the ignition system is set up OK. But, it
should be checked again ... I just went through hell adjusting mixture when
it was really old points and a fouled plug.
I agree with Scott that a lifted piston means too much air is flowing.
However, it can't be a leak in the usual place (throttle plate shaft,
vacuum hose (front carb, remember), or carb/intake gasket. This wouldn't
raise the piston, right? It has to be air flowing >through< the normal
air intake.
My guesses relate to the throttle plate:
1) the plate itself has rotated on the shaft (in my carbs their are two
screws which lock down the plate. You can loosen those and move the
plate in relation to the external linkage). Maybe it is loose, which
might cause unexplained variations.
2) My carbs have little spring-loaded valves in the throttle plates.
When you let off the loud pedal, these valves are supposed to open to
prevent over-rich operation in a trailing throttle situation. If the
spring has disappeared or fatigued, there will be more air admitted at
idle.
3) Marcus hasn't balanced the carbs by loosening the throttle linkage,
balance with the idle screws, then retightening.
(I am >sure< he did this. Right?)
4) Carb Throttle return spring is limp, too long, or missing (Naah).
Many of Marcus' misfiring problems remind me of overlean mixture.
Backfiring through the carbs, as opposed to the tailpipe, for instance.
Hope these WAGs spark a solution.
...John Trindle (jtrindle@ftf03.larc.nasa.gov)
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