Vacumn advance
Kerry D
give you the same results for distributor advance as coming from carb
fitting?
Dwain G.
vacuum.
Manifold vacuum exists at the fitting you mentioned because it is below, or
beyond the throttle plates of the carburetor. It is at its maximum at idle
speed and drops off sharply when the throttle is opened.
Ported vacuum, where the vacuum advance connects, is above the throttle
plates, and should read (nearly) zero at idle speed, but increases sharply
as the throttle is opened.
Dwain G.
Sonny
advance at all times when the car is running. It also holds the diaphragm in
the fully retracted position, so if your engine is producing the normal 16
to 18 inches of vacuum it can damage the diaphragm very quickly, and
advances the timing to full advance all the way from start to cruise, which
is not correct. Especially when starting the engine, you do not want timing
advance. The correct carburetor fitting will only give vacuum or advance as
the throttle is pushed down, in varying amounts, as the vacuum advance was
designed, which is correct.
Unless your shop manual specifically tells you where to put the vacuum
advance line, always put it to a carburetor fitting. Note: Some carbs have
more than one vacuum fitting. To find the correct carb fitting easily, block
the carb fittings off with rubber caps or pieces of hose with screws in
them, start the engine and let it idle, remove the caps one at a time. If
you can feel vacuum with your finger while the car is idling, or the engine
changes rpm when you remove the cap, that is the WRONG fitting.
Normally you will find the correct connection on the base in the front of
the carb, near the air mixture screws, or on the passenger side, (choke
side), in the area of the carb in front of the choke. Since the correct
connector will have no vacuum until you increase the engine rpm, the obvious
test is the increase in vacuum will be able to be felt with your finger.
Also, automatic chokes normally have a fitting or fittings going to the
intake manifold to draw heat from the intake to warm the choke. That fitting
normally has no vacuum, and is a very big fitting, has threads, and is very
obviously NOT the right connection. The correct connection to the carb you
are looking for is about the same size or diameter as the connection on the
vacuum advance and does not have threads. I have seen earlier carbs with
metal lines and compression fittings on both the vacuum advance and carb
ends, especially early Ford, Jeep, Chrysler, but it's very easy to figure
out where those lines connect. Hope this helps.
Sonny
"Kerry D" <stude...@yahoo.com> wrote in message
news:ad370fde.03011...@posting.google.com...
Jeff Rice
If it were, you'd have the advance plate at full advance at idle (high
vacuum) and when you stepped on the gas (drop manifold vacuum) the timing
would retard. Then the timing would advance again with the centrifugal
weights.
It would act wierd, start hard, and not run well.
Carb vacuum taps into a port drilled right in the venturi ring of the carb.
Bernoulli's principal says that as cross section in a tube decreases, the
velocity increases, and the pressure decreases.
This is how the carb gets the fuel into the manifold. The engine doesn't
suck the fuel in, the outside ambient air pressure pushes the fuel into the
low pressure are right at the venturi rings of the carb.
This same area (at the narrow point of the venturi rings) then can be tapped
for a vacuum signal that tells the distributor approximately how much air
(mixed with fuel) is going into the engine. That can be calibrated to get
the distributor to advance the timing to make sure the spark has enough lead
time to light the fuel/air mixture in the cylinder. Since the burn rate of
the fuel and air is fairly constant, you need to light it earlier to get the
pressure buildup from the fuel burning process to peak at exactly the right
time to put the maximum push on the piston to get the most work out of it.
Hope it helps.
Jeff (love that Bernoulli guy ) Rice
"Kerry D"wrote:
Sonny
also like the vernacular. <G> When we ever meet, I'm gonna have to remember
to ask you about a couple of real pressing questions that have always nagged
me about the effect that certain wing tip dihedrals might contribute to
vortices and drag coefficients. <G>
Sonny
"Jeff Rice" <DEEPNHOCK...@worldnet.att.net> wrote in message
news:82%T9.106314$hK4.8...@bgtnsc05-news.ops.worldnet.att.net...
Freddy Badgett
horzontal plane?
Freddy
JETman
Taylor" aura. Last year at the big meet in SB, I tripped over a
disoriented King snake just after meeting him and when I attempted to
get up, I hit my head on a 1930's era bumper and went down again only to
have a 350 lb. lady step on me on her way to nearest porta-potty... And
the risk rises about tenfold if Calvin is with him!
Wear a helmet and shin/elbow guards and safety glasses and....
<seg>
JT
--
Regards,
JT (Residing in Austin, Texas)
Just Tooling Down The Internet Superhighway With my G4.......
Kerry D
has no vacumn port? Does that mean I can only run mechanical advance?
This is a racing carb with no choke. Running another "chokeless" one
at the moment that idles great and only takes 50 or 60 seconds to warm
up in 50 degree weather before going on my merry way. I would never
have believed it and thought it would be a bitch before installing it.
"Sonny" <X50st...@adelphia.net> wrote in message news:<Ac_T9.80342$VA5.11...@news1.news.adelphia.net>...
Sonny
Sonny
"Freddy Badgett" <bbad...@triad.rr.com> wrote in message
news:3E2093E7...@triad.rr.com...
Jeff Rice
A Holley? AFB? Fish?
If it's a Holley, you can download their manuals at:
http://www.holley.com/Catalogs/Catalogs.html
Ran into this website... It may help you out.
http://www.projectbasketcase.com/info/trouble.html
http://www.projectbasketcase.com/info/vacuum.html
Sonny
game!
Sonny
"JETman" <jeta...@worldnet.att.net> wrote in message
news:3E2096D5...@worldnet.att.net...
Sonny
mechanical advance?<
Yep, that's what I would recommend. There is a kit available to put springs
and weights in the distributor that will, "kinda" give you incremental
advance. I say kinda because they are normally just in and out of full
advance at a pre-determined rpm, but it's STILL a better situation than full
vacuum to the vacuum advance. Some race cars used magnetos, and the newest
hi-tech racing cars don't even use a distributor.
> This is a racing carb with no choke. Running another "chokeless" one at
the moment that idles great and only takes 50 or 60 seconds to warm up in 50
degree weather before going on my merry way. I would never have believed it
and thought it would be a bitch before installing it.<
It sounds like you have a typical racing carb that is set up way too rich
for the street and shouldn't be a problem if you make your living on the
street in the highest RPM ranges all the time, are not worried about the 5
mpg or less, and the mean temperature always remains above 50 degrees. <G> A
carburetor that is set up correctly would have a hard time starting and
running smoothly until it was warmed up. Also, running an engine too rich on
the street has other negative consequences especially if you have to cruise
around for a while looking for the other guy willing to lose his pink slip.
<LOL>
Sonny
Jeff Grohs
I put an edelbrock 1406 on my 63 avanti to replace the afb which wouldn't
run right. It's got two vacuum ports. The manual that came with the carb
listed one of them ( not the one I'm using) as "timed". I'm still not
totally happy with the way it runs at lower RPM's. Could this be some of the
problem?
Pat Drnec
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thx
"Pat Drnec" <pat...@drnec.com> wrote in message
news:3E2101CF...@drnec.com...
Sonny
"Jeff Grohs" wrote:
<SNIP>
> I put an edelbrock 1406 on my 63 avanti to replace the afb which wouldn't
run right. It's got two vacuum ports. The manual that came with the carb
happy with the way it runs at lower RPM's. Could this be some of the
problem?<
Very possibly Jeff. Check the vacuum ports to see which one only gives
vacuum when the throttle is opened. That is the port you want. If that
doesen't help, you probably need a combination of timing and carb tuning.
Good tuning is somewhat of an art if you don't have the high tech machinery,
never was an exact science, just take your time, make one change at a time,
test it, note the difference and on and on. Remember of course that some
changes effect some of the settings that you were satisfied with! <G> See
what I mean, no science here.
Have you checked very thouroughly for vacuum leaks around the top of the
engine? It wouldn't hurt anything to get on a tuneup machine that has
exhaust gas analizer capability. Hopefully we can get enough feedback from
everybody trying to do tuning to see what really works.
Sonny
Pat Drnec
of wd-40, or even Gunk engine cleaner. With the engine running, spray
around the carb base and other potential vacuum leaks - if there is one
the idle will change when the spray hits it. Used to use that test after
installing a carb on my 49 Harley, the o-rings for the intake manifold
were a bitch to seat correctly.
Jeff Rice
RPM jumps...found it.
No clean up.
Jeff (sometimes no eyebrows <g>) Rice
JETman
JT
--
Jeff Rice
"JETman" wrote:
> Heh heh... Have you ever used one in a closed garage...