Spica Butterfly Adjustment, was Re: Backfiring (Spica)

["Mr. Leslie Wong" <lesliewong@xxxxxxxxxxx>]

Should the throttle plates on a Spica system be completely closed at idle so
that no air is passing through?

I read in the AROO Tune Up Clinic
(http://www.alfaclub.org/techstff/tunespca.htm) that "The Short Rod must be
set so that there is a slight clearance between the closed throttle plates
and the bores. This clearance prevents the throttle plates from the digging
into the inlet runners when the throttle is snapped shut...The idle speed
can be changed, if necessary, by slightly adjusting the idle stop and/or the
Short Rod." I guess it's this line that is confusing me.

I recently acquired a Syncrometer
(http://homepage.mac.com/lesliewong/synchrometer/synchrometer.htm) to check
the throttle plate synchronization in the intake my 1979 Alfetta Sprint
Veloce. I thought I adjusted the idle limit stop screw per my Ingram manual
instructions.

When I place the Syncrometer in any of the intakes at idle, the gauge reads
about 3 (kg/hr). According to the Ingram Manual, "idle air should not pass
through the butterfly plates." Does this number constitute the small amount
of air due to worn "throttle body seals and shafts due to high mileage"?

The car actually runs fine. There is no backfiring but slight "burbling" if
I don't take my foot off the accelerator completely. It revs willingly past
redline (Crane XR700 ignition). The cold start solenoid and the thermostatic
actuator seem adjusted OK. Car starts on the first turn of the key when
cold, idles 1500-2000 RPM until warm. Starts fast when hot. I get about 27
MPG on the highway, 20 city. Bosch 4477 plugs are good color. New o-ring on
idle barrel.

Thanks,

Leslie Wong
1979 Alfetta Sprint Veloce
Pacific Grove, CA
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