SU Carb Idle Issue

[Duffman]

OK, up front let me say that both my 4 screw SUs have vacuum leaks, have done the leak test and confirmed that there are issues. As I am waiting to accumulate the necessary funds to have Z Therapy work their magic on my carbs, am trying to balance as close as I can get. My front carb allows me to adjust the idle down but my back carb only goes down so far. I can balance both at about 1300 rpm, no lower. I turn the idle screw down on my back carb and it will not go below a certain level. I have cleaned both carbs and adjusted the floats accordingly, as well as lubed the linkage. Just want to confirm that there is nothing else I can do to get the idle down, until I get both carbs rebuilt, am I correct?

[tlorber]

Have you checked the screw that syncronizes the carbs at high speed. If this is too tight, your rear carb may not be actually sitting at idle, but may be tied to the front carb's idle.

[Duffman]

Good point, will double check. Thought I checked this already when I synched the carbs at high idle, but may have missed adjusting the high idle screw back. Anything else I may have missed?

[tlorber]

If the throttle shafts are leaking a lot of air ("a lot" is a relative term), they may be permitting air to pass through that the butterfly would normally close off, thereby rendering your idle adjustment useless.

If funds are your main issue, you may want to ask Bruce about purchasing just the throttle bodies. Assuming the rest of your carbs are good, he can send you the newly bushed throttle bodies, you transfer all of the other components from old to new, and then send in your old ones as the core. This is less than half the cost of the completely refurbished set.

[Duffman]

Thanks, Todd, guess I am thinking about doing the whole rebuild to take advantage of everything that Z Therapy does to make the carbs perfect! Might just have to put up with the high idle. I do have the carbs as balanced as they can be, and the car runs fine, just a high idle.