Doug,
It sounds as though you my have more than one problem. In the past I
worked with the GM three two set up. Of course, I know that you
understand the original configuration by your mentioning that all three
have idle circuits. The original setup used an idle circuit in the
middle carb only, and the end carbs were actuated by vacuum, and were
intended to run only at off idle.
With the setup you are running, I would disconnect the carbs from each
other and try moving off of idle with one at a time to see if there is a
smooth transition to the main circuit. You may find that one or more of
the carbs are stumbling, or even quitting completely, just off of idle
do to lean out. The transition from idle to main jet operation requires
some overlap of the systems. I have found that, if the fuel level is
correct and you still have a problem, drilling the idle tubes just a bit
will cure the problem. Another problem you may have is that with all
three accel pumps working, you may be flooding the system when you come
off idle. Some times lowering the end carburetor fuel levels a fraction
will help also. Getting multiple carburetors to work properly can be a
challenge, I know for when I ran the Desoto, I had six 97 Strombergs on
a Crower "weld it together yourself" log manifold. It idled fine at
900-1000 RPMs.
Tom, Redding CA - #216 D/GCC
Doug Anderson wrote:
>Problem: "She's got two idle speeds boys" -"tto slow 6 hunnert, and
>Seven-TEEN hunnert and only SHE decides WHEN ...and she changes her mind
>pretty reg'lar like. -Jus' like a woman
>
>
>Equipment:
>
>Induction: 3 old 1960s RottenChester 2GC two barrel carbies ( built up from
>seven junkyard refugees ) on a 3 deuce Offenhauser manifold. Set up with
>home built aluminum progressive linkage with spherical rod ends and double
>return springs jus' like ya''saposdta. End Carburetors have idle circuits
>and power valves plugged and deleted, 56 jets(?),Accelerator pumps intact
>and working. Center carb has manual choke, 58 jets (?) and all other
>functions working. All floats set according to spec, with proper gauge -all
>"re-built" and set up over a long winter by your resident genius, the
>writer.
>
>Block: '66 small journal 327 Chevalay block poked to 4.060 (332 c.i.)
>( annybody can have a 350... -"it takes a real man to have a 327" )
>
>Pistons: KB 1966 Hi-Po 327 pop-up type with .12 dome.
>
>Rods: polished n' peened 327 Steel, ARP bolts
>
>Compression ratio: 10 1/4
>
>Crank: .010 /.010 327 polished & detailed throws, Balanced assembly.
>
>Cam: Rumpity, Comp Cams Hydraulic, 490 lift intake & exhaust, w/"losta"
>duration and lotsa lope. Nirvana after 2800 RPM to 8000. :-)
>
>Vacuum; 7 inches @ slow idle, 17 inches @ highway speed.
>
>Ignition: Circa 1969-70 style Delco single point Dizzy with Mallory points
>and condenser triggering a MSD 6A spark box and Blaster coil mounted inside
>car and under the cowl with coil wire sneakin' it's way thru a grommet in
>the firewall. Looks good, runs good, starts good.
>
>
>Driving characteristics: Absolutely Loves WOT but usin' that on the street
>alla time can get you lodging down at the Graybar Motel perty quick like.
>Response at mid range speeds good, -excellent throttle response. Off idle
>response often comes with a "poof" a hesitation but driveable. She don't
>like me to make'er come back to life when she's restin' I'm thinkin'. "The
>Combination" is very susceptible to climatic changes; on sunny breezy days
>she runs like a... well you get the idie. But on days less than ideal,
>-with a touch of "weather" in the air, you're out there adjustin' the idle
>speed because she's changed ...AGAIN.
>
>
>Results of extensive B.Y.* R & D:
>
>Using a slim flashlight, Gas is discovered DRIPPING in an intermittent,
>"occasional" pattern from the left annular discharge nozzle inside the
>center, primary carburetor venturi at idle speed with engine "warmed up".
>When it does, of course the idle speed goes UP then RPM tapers off as gas
>is used up until the next drip that is... While this phenomenon repeats
>itself over and over, the vacuum rises and falls on the Stewart-Warner gauge
>in the dash from 7,( up to maybe 15 inches ?) WHEN this happens you can
>stand yards away from the car and it sounds like there's someone inside
>playin' upsy-downsy with the gas pedal kinda spooky like.
>
>We stressed WHEN because sometimes this phenomena doesn't happen.
>Seemingly, it's tied to colder, damper weather patterns. We realize that
>with a Rumpity cam with a Looooong duration, one often does turn up the idle
>air speed screw to attain a decent idle speed. Does this perhaps, have a
>detrimental affect on the whole enchilada ? As an "aid" to easy
>adjustments, I've soldered a small brass tubing nut onto my idle screw to
>eliminate the need for a screwdriver. We've been operating ( and coping )
>with this setup for 6 years, and 22,000 smiles of drivin'...
>
>
> *BackYard
>
> " If we knew what we were doing, they wouldn't call it Research "
>
> -A. Einstein
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