<VV> New carbs - idle rough

[Vanderlind, Patrick]

Got an issue I can't figure out. Rebuilt my 102 completely including
professionally done carbs. 
 
Background:
Had been breaking it in the last couple of weekends to get all the bugs
worked out of it. The engine has nearly 300 miles on it, new pertronics
ignitor one gapped per the instructions, new Clark's Magwire plug wires, NOS
dist. cap and rotor, and the car is a powerglide and has single exhaust. The
entire fuel system is new - tank, sender, hoses, clamps, fuel pump, etc. It
also has an inline fuel filter. The entire wiring harnass is new. The only
thing that is not new is the coil. It is a fairly new Crane that I had on my
65 Turbo. It worked fine on that car and was only replaced because it was
black and I wanted chrome.
 
Issues:
1) Cold blooded. When I try to start it, it will fire and die. I have to
pump the pedal to keep it running. It takes a couple of minutes of this
before it will idle without killing. Chokes are closed and the pull offs are
new and operational. The Choke thermostats are strong and open fully when
warm. The accelorator pump squirts a nice stream of gas like it is supposed
to.
 
2) Once warm the idle is rough and unacceptable. It jumps around quite a
bit. Looking at my dwell/tach meter the idle changes 100 - 300 RPM
inconsistently. I used a uni-sync to balance the carbs and they are
identical in vacuum at idle. The linkage engages the carbs evenly. Pulling
the linkage shows both carb butterflys starting to move at the same time. 
 
3) The idle mixture screw is set to 1 1/2 turns out. Moving the screw either
way does not improve the rough idle. The fast idle cam is not contacting the
tab once warm like it is supposed to.
 
4) All Vacuum hoses are new and tight. The base insulators are new and the
bolts securing the carb to the head are torqued correctly. The hoses to the
balance tube have clamps attached. The vacuum at the modulator valve is
strong and disconnecting the hose and plugging it does not change the rough
idle.
 
5) Disconnecting the vacuum advance and plugging it does not change the
rough idle. The timing is set to 12 dgrs and with a timing light on the
pully the mark does not bounce around with the idle.
 
6) Once warm, I can run the throttle to about 1500 rpm, hold the linkage
steady and the RPM's will fluctuate. I do feel a slight surge or pulsating
at driving speeds.
 
7) One interesting note - when balancing the carbs I initially placed my
hand momentarily over the throat of the drivers side carb and all of a
sudden the idle smoothed out. It ran smooth for a few minutes and all of a
sudden it was rough again.
 
If anyone has any suggestions on what to do next, please let me know. 
 
 
Pat Vanderlind
62  Monza 900 cvt 102 PG
65 Corsa 180 cpe

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