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The motor was dyno tuned and ran perfectly.
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Could you have the wrong idle jets? You were probably only running on the main jets when it ran on the dyno.
On my car (a CAV), I have the standard dual pumps going to individual pressure regulators & anti-backflow valves. Then the outputs go through a tee and on to a second pressure regulator at the carbs (it came with the carb setup from Inglese). The CAV-supplied regulators are set to a higher pressure than the Inglese one. Somewhere along the line (I think when my engine was dynoed), the diaphram in the Inglese regulator ruptured (I'm guessing they fed it from an FI pump and blew it out) leading to some nasty over-rich conditions. When I noticed raw gas spewing out of the Inglese regulator I knew where the problem was /ubbthreads/images/graemlins/shocked.gif. Anyway, the carbs saw well over the 2.5 or 3 PSI that they wanted, and the plugs were all fouled. One was wet with gasoline. After replacing the regulator and cleaning the plugs, it ran a whole lot better, but still rich. And this was at sea level while it's jetted for high altitude so should have been running lean. In any case, most of my driving was at part throttle so was on the idle jets. Now the weird thing is that I'm told my idle jets are too lean (as indicated by having to back out the idle screws 2 1/2 turns) and that this is what is causing the rich condition. Sounds strange. My car hasn't been touched since August, so I don't have a resolution to my problem yet, but in any case it seems to be the idle jets.
According to
Mickey Lauria:
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On a correctly-jetted idle circuit, the mixture screw on a 48 IDA is never more than 3/4 of a turn out. This will hold true 100% of the time, no matter what anyone else tells you. If you have to go more than that, you'd better heavy-up the idle jet.
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My Webers are IDFs, but still 2 1/2 turns is too much...
So... How far do you have to back out your idle screws?