four-barrel setting

Vacuum secondaries will come on when you demand enough to cause them to.
Mechanical secondaries will come on based on the the throttle position. RPM
has nothing to do with either.

"Mike Harrison" <mike_harrison80.DeleteThis@yahoo.com> wrote in message
news:8f23da36.0408131837.1d377770@posting.google.com...
 > Hello group, hopefully a simple question:
 > For a four-barrel carb, at what RPM setting should the 3&4 barrels be
 > set to open at? For example should they open when attempting to climb
 > onto plane, and then once on plane, throttle back and plane with only
 > 1&2 open?<!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: four-barrel setting 

I dunno but here's about how mine (Rochester Q-jet) works which seems ok to
me. From a stop (alpha outdrive) with trim all the way down, I open the
throttle at say a count of 1000, 2000, 3000. With the trim down, the boat
comes up onto plane flat ... the bow does not point up. At about 2300 rpm I
am on plane and around about 2400 rpm (since the engine's under load) I hear
the secondaries opening (and if I go out tomorrow I'll check that) . If I'm
just going to cruise, I throttle back to about 2300 rpm while simultaneously
setting the trim for best speed/rpm which works out to engaging the trim
(up) button for about a second (count of say 1000). And from that point on,
I won't hear the secondaries open unless operating close to WOT which is
about 4000 rpm with the 23" prop and about 4300 rpm with the 21"prop. So,
for me I'd say it's about 2400 rpm coming onto plane but I'll check that
next time out.

"JamesgangNC" <jamesgangnc RemoveThis @nospam.com> wrote in message
news:1vvTc.25362$Jp6.18961@newsread3.news.atl.earthlink.net...
 > Vacuum secondaries will come on when you demand enough to cause them to.
 > Mechanical secondaries will come on based on the the throttle position.
RPM
 > has nothing to do with either.
 >
 > "Mike Harrison" <mike_harrison80 RemoveThis @yahoo.com> wrote in message
 > news:8f23da36.0408131837.1d377770@posting.google.com...
  > > Hello group, hopefully a simple question:
  > > For a four-barrel carb, at what RPM setting should the 3&4 barrels be
  > > set to open at? For example should they open when attempting to climb
  > > onto plane, and then once on plane, throttle back and plane with only
  > > 1&2 open?
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: four-barrel setting 

Unless you are watching them you really don't know when 4 barrel secondaries
are open or how much. Quadrajets make a noise when you open the throttle
wide at lower rpm's and you hear the extra air flow on the secondaries. But
gently opening the throttle to increase speed can result in the secondaries
opening some and not making any noticable difference in sound.


"Bowgus" <bowgus.TakeThisOut@rogers.com> wrote in message
news:pWxTc.1712281$Ar.857211@twister01.bloor.is.net.cable.rogers.com...
 > I dunno but here's about how mine (Rochester Q-jet) works which seems ok
to
 > me. From a stop (alpha outdrive) with trim all the way down, I open the
 > throttle at say a count of 1000, 2000, 3000. With the trim down, the boat
 > comes up onto plane flat ... the bow does not point up. At about 2300 rpm
I
 > am on plane and around about 2400 rpm (since the engine's under load) I
hear
 > the secondaries opening (and if I go out tomorrow I'll check that) . If
I'm
 > just going to cruise, I throttle back to about 2300 rpm while
simultaneously
 > setting the trim for best speed/rpm which works out to engaging the trim
 > (up) button for about a second (count of say 1000). And from that point
on,
 > I won't hear the secondaries open unless operating close to WOT which is
 > about 4000 rpm with the 23" prop and about 4300 rpm with the 21"prop. So,
 > for me I'd say it's about 2400 rpm coming onto plane but I'll check that
 > next time out.
 >
 > "JamesgangNC" <jamesgangnc.TakeThisOut@nospam.com> wrote in message
 > news:1vvTc.25362$Jp6.18961@newsread3.news.atl.earthlink.net...
  > > Vacuum secondaries will come on when you demand enough to cause them to.
  > > Mechanical secondaries will come on based on the the throttle position.
 > RPM
  > > has nothing to do with either.
  > >
  > > "Mike Harrison" <mike_harrison80.TakeThisOut@yahoo.com> wrote in message
  > > news:8f23da36.0408131837.1d377770@posting.google.com...
   > > > Hello group, hopefully a simple question:
   > > > For a four-barrel carb, at what RPM setting should the 3&4 barrels be
   > > > set to open at? For example should they open when attempting to climb
   > > > onto plane, and then once on plane, throttle back and plane with only
   > > > 1&2 open?
  > >
  > >
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: four-barrel setting 

I suppose a seat of the pants way to determine when the secondaries open
when coming onto plane would be to lock the secondaries shut ... do a run
.... then unlock the secondaries and do a run ... and compare. And I guess
the secondaries spring adjustment would be the best place to start playing
to get the opening point you want. My acceleration is smooth .. no bogging
.... all the way from idle to WOT so I'm leaving well enough alone.

OT: And so far, the float stuck open only once this season which was on
dewinterizing ... last season it stuck a few times ... I was not looking
particularly forward to replacing the needle and seat. No big deal ... it's
just that more often that not, one simple repair leads to another more
costly one, and so on.


"JamesgangNC" <jamesgangnc.RemoveThis@nospam.com> wrote in message
news:ujKTc.25867$Jp6.3619@newsread3.news.atl.earthlink.net...
 > Unless you are watching them you really don't know when 4 barrel
secondaries
 > are open or how much. Quadrajets make a noise when you open the throttle
 > wide at lower rpm's and you hear the extra air flow on the secondaries.
But
 > gently opening the throttle to increase speed can result in the
secondaries
 > opening some and not making any noticable difference in sound.
 >
 >
 > "Bowgus" <bowgus.RemoveThis@rogers.com> wrote in message
 > news:pWxTc.1712281$Ar.857211@twister01.bloor.is.net.cable.rogers.com...
  > > I dunno but here's about how mine (Rochester Q-jet) works which seems ok
 > to
  > > me. From a stop (alpha outdrive) with trim all the way down, I open the
  > > throttle at say a count of 1000, 2000, 3000. With the trim down, the
boat
  > > comes up onto plane flat ... the bow does not point up. At about 2300
rpm
 > I
  > > am on plane and around about 2400 rpm (since the engine's under load) I
 > hear
  > > the secondaries opening (and if I go out tomorrow I'll check that) . If
 > I'm
  > > just going to cruise, I throttle back to about 2300 rpm while
 > simultaneously
  > > setting the trim for best speed/rpm which works out to engaging the trim
  > > (up) button for about a second (count of say 1000). And from that point
 > on,
  > > I won't hear the secondaries open unless operating close to WOT which is
  > > about 4000 rpm with the 23" prop and about 4300 rpm with the 21"prop.
So,
  > > for me I'd say it's about 2400 rpm coming onto plane but I'll check that
  > > next time out.
  > >
  > > "JamesgangNC" <jamesgangnc.RemoveThis@nospam.com> wrote in message
  > > news:1vvTc.25362$Jp6.18961@newsread3.news.atl.earthlink.net...
   > > > Vacuum secondaries will come on when you demand enough to cause them
to.
   > > > Mechanical secondaries will come on based on the the throttle
position.
  > > RPM
   > > > has nothing to do with either.
   > > >
   > > > "Mike Harrison" <mike_harrison80.RemoveThis@yahoo.com> wrote in message
   > > > news:8f23da36.0408131837.1d377770@posting.google.com...
   > > > > Hello group, hopefully a simple question:
   > > > > For a four-barrel carb, at what RPM setting should the 3&4 barrels
be
   > > > > set to open at? For example should they open when attempting to
climb
   > > > > onto plane, and then once on plane, throttle back and plane with
only
   > > > > 1&2 open?
   > > >
   > > >
  > >
  > >
 >
 ><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: four-barrel setting 

  > > "JamesgangNC" <jamesgangnc.DeleteThis@nospam.com> wrote in message
  > > news:1vvTc.25362$Jp6.18961@newsread3.news.atl.earthlink.net...
   > > > Vacuum secondaries will come on when you demand enough to cause them
to.
   > > > Mechanical secondaries will come on based on the the throttle
position.
  > > RPM
   > > > has nothing to do with either.

Not entirely correct...only if the weight, or drag changes on the boat.

Because water is the same thickness, and always flat, there is no load
change to effect vacuum secondaries...unless one of the previous mentioned
situations are present.

Vacuum secondaries (on a boat motor) will always open at the same RPM every
day, in relation to throttle position, unless there is more...or less
resistance.

This is also why boat engines don't need vacuum advances...the never go
"uphill", or operate in pea soup.


--
-Netsock

"It's just about going fast...that's all..."
<a style='text-decoration: underline;' href="http://home.insight.rr.com/cgreen/" target="_blank">http://home.insight.rr.com/cgreen/</a><!-- ~MESSAGE_AFTER~ -->
 >> Stay informed about: four-barrel setting