You CAN'T use the vacuum retard unit on any carb other than
the original Stgromberg! !!
This vacuum retard unit needs a special type of ported vacuum connection
which supplies full vacuum at idle, and zero vacuum as soon as
you apply any throttle at all.
The intent is that you get the full retard only during idle (for NO2
emissions, presumably). The rest of the time it has no effect.
When I installed HS2s on my '72, I left the vacuum retard unit disconnected,
and I did NOT adjust the timing. Now I get more or less +8 deg.
at idle, which is theoretically "wrong", but I get the correct advance
the rest of the time. (And it idles just fine).
A "normal" ported vacuum gives zero vacuum at idle, max vacuum
at part throttle, and zero again at full throttle. This
makes sense for a vacuum ADVANCE unit: You get max advance
at part throttle for economy, less advance at full throttle
to avoid knocking, and less advance at idle for emissions.
But if you hook up the vacuum retard unit to this, it will
certainly act wacky.
In my case, I could presumably install a proper vacuum advance unit,
and hook it to my SUs. Then I would probably get better gas mileage,
but I would NOT get any more full-throttle power...
Doug Braun
'72 Spit
P.S.: The Benteley manual has a bunch of tables and charts
for the various distributors and advance units.
At 10:04 AM 8/11/00 -0400, you wrote:
>Well after a tedious 2 hours I believe I like the way they are balanced.
>throttle stops, choke, high idle steps...all look/feel great to me.
>
>My floating idle.... got rid of that flaky vac. retard..
>
>The vac retard unit was not hold a vac between 0 and -10psi. It would 'bleed
>down'
>Below -10psi it would hold fine.
>So... while mildly accelerating 95-10 psi vac) the ignition timing would float
>around +/- 5 degrees.
>the hole must seal up above 10 psi of vac because at these levels it will hold
>the position.
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