I'm having a bit of an issue tuning my Holley to get a good idle with smooth transition from off the gas to on, the pedal is more like a switch either on or off! which doesn't make it much fun around town, trying to trickle along it feels rich but on the gas it pulls like a train. Could it be the float level?

 Does it have a "bog", or hesitation when you first give it gas to accelerate? If so, I would first look at the accelerator pump and cam for proper operation/calibration. Check your ignition timing also.
From there I would have to say the thing needs to be cleaned/rebuilt.

If removing the air cleaner changes the idle speed, then the carb has a problem.
The good news about Holley carbs are they have a lot of adjustments.  The bad news is they have a lot of adjustments. 

Not so much a bog but if I press gently on the pedal nothing happens at first then the power comes on in a rush making it very difficult to drive slowly like when in traffic around town.
I'm doing a parade today in a local carnival so that should be fun (not!) but I promised so I can't let them down!
Thanks
Graham
PS Its a List 6619-1 Holley which I believe is an emmissions carb from the 70's whatever that means!


|UPDATED|7/2/2016 2:11:06 AM (AZT)|/UPDATED|

Is it a spreadbore or a squarebore?

Not really sure of the difference, it's on a performer inlet, any way my last tweaking a seem to have been more successful as she behaved very well yesterday in the carnival procession covering a few miles at a snails pace with a celebrity guest in the car with me, pulled steadily at 500-750 rpm even up hill and idled happily when stopped. I had an issue recently when checking timing with my dial back timing light which showed the timing badly retarded but after stripping off the pulleys to check the damper all seemed to be in order so my timing light must have been playing tricks on me! I will rebuild the carb as its weeping a bit of fuel from a couple of places, nothing too serious but needs doing. Thanks for your help Graham

Spent yesterday rebuilding my Holley, the diaphragm was porous on the accelerator pump which explained the weeping leak, everything else looked OK, quite clean inside which I was a little surprised about so the filter must be doing its job!