So,
>the question is whether the engine is advanced or retarded as the vacuum
>decreases or increases at idle speed.
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This can be kinda complicated. It CAN be both ways. If the vacuum
mechanism has a port on both sides of the diaphragm housing, then you can
either advance or retard the timing, depending on which port sees the
vacuum at any given time If it has only one port on one side of the
housing, then it can be EITHER an advance or retard mechanism. It then
depends upon which side of the diaphragm the port sees.
It's been my experience that when you look at the diaphragm housing, and
the port is on the side facing AWAY from the body of the distributor, then
the mechanism ADVANCES the timing when activated. If however it's situated
on the side FACING the body of the distributor, then it would retard the
timing at idle.
Barry Schwartz (San Diego) bschwart@pacbell.net
72 PI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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