> The vacuum ADVANCE distributor is advanced mechanically as a function
> of RPM, and manifold vacuum is used to provide additional advance,
> depending on the load (as measured by manifold vaccum). The vacuum is
> higher when the load is lower i.e. crusing, or idling, and lower for
> heavly load, i.e. accelerating, long uphill climbs.
Actually, I _believe_ its the other way 'round. Vacuum increases with
engine load, i.e., high vacuum when accelerating, lower vacuum when
idling or at constant RPM.
This is due to the fact that the pistons trying to pull air through the
restriction of the carb/butterfly. The higher the RPM, the more air they
need to pull in, therefore higher vacuum in the manifold. Vacuum is
highest when accelerating because the air in the manifold has a given
inertia which must be overcome before it may move more quickly
into the combustion chamber.
Dave Williamson (Silikal@aol.com)
'68 & '69 Spit bodies / '68 Spit, '71 GT6+, & '73 GT6 drivetrains
_5_ years into frame-off restorations, nothing _close_ to done
(so many Triumphs, so little time)
PS - I've unsubscribed until 1/5/94 for vacation so
flame by e-mail only. 8-)
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