"Bob,
While there are/were cars which worked that way
(Ford 6s, some VWs, and others with no centrifugal
advance), most carburetors have a single advance =
port located just above the throttle plate at idle on
the side which opens upward. With the throttle closed,
(idle, deceleration) there is NO vacuum advance at all.
As soon as you begin depressing the throttle, the throttle
plate starts uncovering the vacuum advance port, until
at about 1/8 throttle it sees roughly manifold vacuum.
=46rom then on you have essentially manifold vacuum
to your advancer. This signal varies ~inversely
with engine load. This port is well below the
venturii(s) in the carburetor, so I doubt there is much
Bernoulli effect on the signal."
Thanks for the post
Had I seen it sooner (If I wasn't on the digest) I wouldn't
have posted on the port vacuum issue
Regards
Gary Zingle
1973 GMC 26 foot =
While there are/were cars which worked that way
(Ford 6s, some VWs, and others with no centrifugal
advance), most carburetors have a single advance =
port located just above the throttle plate at idle on
the side which opens upward. With the throttle closed,
(idle, deceleration) there is NO vacuum advance at all.
As soon as you begin depressing the throttle, the throttle
plate starts uncovering the vacuum advance port, until
at about 1/8 throttle it sees roughly manifold vacuum.
=46rom then on you have essentially manifold vacuum
to your advancer. This signal varies ~inversely
with engine load. This port is well below the
venturii(s) in the carburetor, so I doubt there is much
Bernoulli effect on the signal."
Thanks for the post
Had I seen it sooner (If I wasn't on the digest) I wouldn't
have posted on the port vacuum issue
Regards
Gary Zingle
1973 GMC 26 foot =
