Carb Idle Stops

Yes, but they have nothing to do with being a throttle stop. On that end of the 1-2 carb there is a bracket holding a microswitch (for the R2 points operation) that is actuated by the paddle on the end of the 1-2 carb throttle shaft -- here are a couple of examples:
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The throttle stops for the 1-2 carb and the 7-8 carb are as shown here:

http://ferrarichat.com/forum/showpost.php?p=138843300&postcount=14

 

Never a bad thing to make sure that the throttle shaft return spring (on both the 3-4 and 1-2 carbs) is working well, but the test that you are making is invalid as described in the jpeg. As you turn that screw back in, the 3-4 carb should start to close -- keep turning that screw back in until the 3-4 carb is making contact with its throttle stop:

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Or, to state it differently, if you had the engine running and the 3-4 carb was at 10 kg-hr, but the 1-2 carb is at 4 kg-hr, turn that screw inwards until the 1-2 carb is flowing the same as the 3-4 carb. Then use the 3-4 idle stop screw to set the (now equal) 3-4 carb flow and 1-2 carb flow simultaneously to the desired value.

 

Speaking of 308 carburetor adjustments, I have a 77 GTB that idles a bit low with the AC on, around 600-700rpm. With AC off it's fine, around 900rpm. With AC on and engine warm it tries to die, requiring constant input of my right foot to keep it alive.

What's the best, simple way to raise my idle a few hundred RPM? I've got them all synched really nice, car runs great. A few summers ago I raised the idle a bit to compensate for AC drag, forgot how I did it, would like the best advice, if possible..

Of course, once cool weather arrives, with the AC off, my idle will then be too high, oh well..! These cars have no AC idle circuit, right?

Thanks,
Greg

 

I'd suggest that you bring the other three carbs up to 3.5 kr/hr, and get closer to the 1000 RPM nominal idle spec -- JMO.

 

Steve, I'd love your advice regarding post #8...

Thanks,
Greg

 

Is there one?

Seriously, to raise the RPM, you really need to increase the airflow entering all the carbs equally so this implies remeasuring with the Synchrometer to make sure that they are all still quasi-equal after the adjustments. On a well-synced set-up, this could be as simple as just turning the idle stop screw on the 3-4 carb throttle shaft and the idle stop screw on the 5-6 carb throttle shaft equal amounts. If you've got a long screwdriver, you might be able to do this, and I think the Synchrometer nozzle will fit/seal into the airhorns so you might be able to get away with just taking the top of the air cleaner off rather than the whole thing -- if your air cleaner top will come off without removing the engine bonnet (I can't recall if mine would or wouldn't) and the Synchrometer clears the bonnet -- but it may not.

However, if the airflow is increased, you might need to also retweak (slightly open) the mixture screws to keep the idle A/F ratio where it should be.

 

Don't really have anything too specific in mind, but maybe one thing you should do is make sure that the exhaust system is well-sealed with no leaks (except at the tailpipes ) -- at the gaskets (header-to-cyl. head and donuts), in the air injection system hardware, at the header exhaust sampling tubes/plugs, etc..