Chris,
As Stan points out the reason there is no vacuum advance on
the Solex set-up is likely because the carbs available at
the time didn't provide a vacuum port.
However; I believe the Solex set-up would benefit from a
vacuum advance, but not for high rpms. The vacuum system
provides advance (6 degs?) only during light load (partial
throttle), if I recall the exhaust gas tends to dilute the
mixture under these conditions. The additional advance
provides more power, but the real benefit is better gas
mileage. If this advance were added to the mechanical
advance at WOT (where cylinder filling is optimized)
detonation & burned pistons are likely.
BTW, the increased initial timing on the Solex setup is to
take advantage of the improved volumetic efficiency, in
addition I believe providing the mechanical advance earlier
(distributor re-curve) may also increase power. I suspect
the roadster racers out there have some experience with
this. Of couse one needs to be wary of detonation here as
well.
Check out Jason Gray's excellent write-up on adding a vacuum
advance, et al., to a Webber equiped 510.
http://home.att.net/~jason510/weber.htm
Todd Osborn
68 2L DATSFUN (dieing for me in install the Solex)
San Jose, CA
On Mon, 12 Feb 2001 09:25:10 -0600
"Chris Robertson" <ckrobertson@hotmail.com> wrote:
> Why does the U20 with a solex setup use a distributor
> with no vacuum
> advance? Is it because static timing is set to 20
> degrees? I would think
> that it could still benefit from more advance at high
> rpms. Gordon?
> Amyone?
>
> Thanks,
> Chris
> _________________________________________________________________
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